Even if a friend posts negative comments about someone you know, its best to avoid getting involved in this behavior.
a) true
b) false

The answer here is true because even though its your friend, you dont want t get part of that beef (sorry just saying), also it is always good to be the better person and engaging in that type of behavior would just make you just as immature as the person who sent the comment. The best course of action be to ask your friend to confront the person who said the comment and ask him r her why they said the comment and try to work it out in a civilized manner, if that doesn't work then you and your friend should just move on with your lives because it would be immature to dwell on something as little as this