How concerned should Buddhists be with the actions of others? Even as I find peace and contentment in observing the 5 precepts and following along the 8 fold path, I realize I sometimes unintentionally benefit from those who don't live in this manner. For example  a friend takes something that wasn't freely given and shares it with me or a nearby person kills the insect flying around that I was trying to ignore. If I have not encouraged people to do such, should I be concerned about their actions or remain concerned only with my own intentions and actions?
I am going to quote Jack Kornfield's Living Dharma, specifically the interview portion with Achaan Chaa, excerpt from the question of &quot;If putting everything together in our bowls is important, why don't you as a teacher do it yourself?&quot; (page 42 to 43 of my edition):

Wisdom is for yourself to watch and develop. Take from the teacher what is good. Be aware of your own practice. If I am resting while you must sit up does this make you angry? If I call the color blue red or say that male is female, don't follow me blindly.
[…] If you watch others at most ten percent of the time and watch yourself ninety percent, this is proper practice. […]
Looking outside the self is comparing, discriminating. You will not find happiness that way. Nor will you find peace if you spend your time looking for the perfect man or the perfect teacher. The Buddha taught us to look at the Dharma, the truth, not to look at other people.

So I would say that, based on this, the lesson here is to remain focused on your own intentions and actions, but to strive to fully notice your own reactions to what happens. If someone else kills the insect and you benefit, how does that make you feel? How do you respond to it?
I would argue that goes even if you have encouraged them not to do it.