Discussion with a Buddhist about jihad in Islam
Question

                I am participating in an email argument about recent events in the war in Afghanistan, and the person who I am arguing with has made the following claim: 

"All Muslim clerics who are true to Islamic/Mohammad teaching preach that anyone other than Muslims are infidels and subject to the sword."

 I don't believe this claim, but I am not a Muslim, and I know very little about Islam, so I don't have the facts to counter this person's claim. What is the Islamic truth here? How should I argue?.
Praise be to Allah.
    Your question to is indicative of a sincere desire to find 
    out the truth, but before that did you not ask yourself: why am I content 
    with this little that I know about Islam? Why don’t I get the full picture 
    about this religion from its followers, even if that means that I have to 
    travel to them? People often travel to earn money or for pleasure, or for 
    other material purposes, or even for foolish purposes. 

    It is the matter of one’s eternal destiny. Is it not possible 
    that this truth that you are seeking is to be found in that which you do not 
    know about Islam? 

    It is even more serious than that, for it is the matter of 
    eternal Paradise or eternal Hell. 

    But in addition to that sincere desire to discover the truth, 
    you also need an even more sincere desire to follow it and the will power to 
    adhere to it, even if it runs contrary to what you were accustomed to 
    before. 

    Moreover, by asking this question you seem to be like a sick 
    person who looks at the surgeon’s knife and its sharpness, and forgets the 
    disease that is killing him, or curses the cautery for its burning and 
    forgets the leprosy that is consuming him. This is not the way of the wise. 

    First of all you should understand the motives for jihad in 
    Islam, before asking about who deserves to be killed. 

    These motives were summed up by Rib’i ibn ‘Aamir and other 
    companions of the Prophet  (peace and blessings of Allaah be upon him) 
    and were stated to Rustam, the commander of the Persian army, in the battle 
    of al-Qaadisiyyah, when he asked them one after another, for three 
    consecutive days before the battle took place: “What is this that you have 
    brought?” The answer came: “Allaah has sent us to bring forth whomsoever He 
    wills from the worship of people to the worship of Allaah alone, from the 
    hardship of this world to its ease, from the injustice of other religions to 
    the justice of Islam. He sent His Messenger with His religion to His 
    creation. Whoever accepts it from us, we will accept it from him and will go 
    back; we will leave him and his land alone. Whoever refuses, we will fight 
    him until we end up in Paradise or in victory.” 

    This religion has always – and continues to and always will – 
    be faced with resistance based on deviant beliefs and false ideologies, with 
    political, military, social, economic and racial obstacles. All these 
    obstacles combined may produce an attitude that rejects Islam altogether and 
    prevents people from following it.  
If verbal discussions 
    and debates, arguing in a way that is better, address deviant beliefs and 
    ideas, then the jihad movement addresses other, material obstacles, foremost 
    among which is the political power that is based on those combined factors. 
    It aims its strikes at the military and political powers that enslave the 
    people to something other than Allaah – i.e., rules them by means of 
    something other than the laws of Allaah – and that prevent them from 
    listening to the truth and following it with absolute freedom. Thus there is 
    a need for both da’wah and jihad in order to face the real obstacles of 
    life. 

    See Ma’aalim fi’l-Tareeq, p. 59 ff 

    Thus it becomes clear that the basic principle of fighting as 
    prescribed in sharee’ah is jihad, and its purpose is that all religion 
    should be devoted to Allaah, and that the word of Allaah should be supreme. 
    Whoever tries to prevent that is to be fought, according to the consensus of 
    the Muslims. With regard to those who are not involved in resistance and 
    fighting – such as women, children, monks, old men, the blind, the 
    chronically ill, and so on – they are not to be killed, according to the 
    majority of scholars, unless they fight in word or deed… because we are to 
    fight those who fight us, if we want the religion of Allaah to prevail, as 
    Allaah says (Interpretation of the meaning): 
“And fight in the way of 
    Allaah those who fight you, but transgress not the limits. Truly, Allaah 
    likes not the transgressors”

    [al-Baqarah 2:190]

     It was proven that our Prophet  (peace and blessings of 
    Allaah be upon him) passed by a woman who had been killed in one of his 
    battles, and the people were standing around her, and he said: “This one was 
    not a fighter.” And he sent a man to Khaalid ibn al-Waleed – who was a 
    general at the head of his army – and commanded him: “Tell him not to kill 
    any children or hired workers.” Perhaps what is meant is those who were not 
    bearing arms. Narrated by Abu Dawood, 2669; al-Albaani said: It is hasan 
    saheeh; Saheeh Abi Dawood, 2324. 
Allaah has permitted 
    killing to whatever extent it is needed to bring people to the right path, 
    as He says (interpretation of the meaning): 

    “and Al‑Fitnah (tumult and oppression) is worse than 
    killing”

    [al-Baqarah 2:217] 
i.e., although killing 
    involves evil and mischief, the evil and mischief caused by the fitnah of 
    the disbelievers (the tumult and oppression that they cause) is worse than 
    that. With regard to the person who does not try to prevent the Muslims from 
    establishing the religion of Allaah, his disbelief harms no one but 
    himself. 

    Al-Siyaasah al-Shar’iyyah by Ibn 
    Taymiyah, 165-167. 

    Here there is an important point to be made: fighting, 
    aggression and oppression are old problems that affect mankind so long as 
    people are influenced by greed and by whims and desires, and so long as both 
    good and evil exist among men. Ibn Khaldoon said:  

    “Wars and all kinds of fighting have existed from the moment 
    Allaah created mankind. Their origin is the desire that some people have to 
    wreak vengeance on others… This is something natural in man and no nation or 
    era is free of this...” 

    Moreover, what do the Muslims have to do with the terrible 
    wars that have taken place between various Christian groups in the past, and 
    what befell the Protestants at the hands of the Catholics? 

    What do the Muslims have to do with the two World Wars, or 
    with Hiroshima and Nagasaki? 

    We have the right to say, along with Count Henri de Christie: 
    “It is more correct to say that the peaceful nature and gentleness of the 
    Muslims is the reason why their state fell.” 

    Allaah the Almighty has spoke the truth: 
“Those who have been 
    expelled from their homes unjustly only because they said: ‘Our Lord is 
    Allaah.’ For had it not been that Allaah checks one set of people by means 
    of another, monasteries, churches, synagogues, and mosques, wherein the Name 
    of Allaah is mentioned much would surely, have been pulled down. Verily, 
    Allaah will help those who help His (Cause). Truly, Allaah is All‑Strong, 
    All‑Mighty”

    [al-Hajj 22:40]

    Think about that, then listen to the words of the Prophet 
     (peace and blessings of Allaah be upon him): “Allaah wonders at those 
    who will enter Paradise in chains.” (Saheeh al-Bukhaari, 3030). And 
    he said: “[The verse] ‘You are the best of peoples ever raised up for 
    mankind’ [Aal ‘Imraan 3:110] means, You are the best for the people, as 
    you bring them with chains on theirnecks till 
    they embrace Islam” (Narrated by al-Bukhaari, 4557) – i.e., when they fight 
    others, they may take some of them prisoner, or others may submit to their 
    rule, then they come to know Islam and enter into the faith, even though 
    they disliked it at first. 

    Perhaps if you do that, you will kiss the hand of the doctor, 
    even if the scars of his scalpel are left on your skin. 

    And Allaah is the Source of strength.