As a Buddhist how do I get over hatred towards my previous religion? I am filled with genuine hatred towards my previous religion. My hatred is not directed towards other religions it's just towards my past. And this constantly bubbles up during meditation.

I don't live in a majority Buddhist country and it was a long hard journey to arrive at the Dhamma. 

I don't have any problem with them following their respective paths but I am filled with rage for all the lies that were filled in my head for their own greed and ignorance. I get so enraged when I see people around me preaching non-sense theology to other people and to what effect, only to fulfil material desires.

So, what is the strategy when you see the lies and ignorance around. Do you keep quiet as not to get into a debate to keep the 'Right Speech' or do you get into arguments?

How do I get rid of hatred and tolerate other people spreading lies?
Think of the followers of your former religion as people who believe that the earth is flat. There's no point getting angry at them. It's ok to argue with them in social circles if you feel it might be useful to some and if you are confident that you can handle it. 

But if it is getting to the point that you start shouting at them or trash talking at them, you should stop and contemplate the Anatta nature of beings. You cannot make other beings think the way you want at will. Meditate on the wanting to control others' thoughts. Whenever anger arises in the mind, simply note it.