Do you feel bad if your friend is a back-stabber?

I think the majority of people have experienced the feeling when a person who is thought to be a good friend back-stabs us. It is a very bad feeling, but I think most of us know it. But I also think that this experiences are somehow useful, because they teach us not to trust blindly in anyone, because it isn't worth it. It is good for a person to have friends, but it is very hard to call them true friends. People change as time changes, a person who today is very nice and can be trusted, has a type of experience which changes him and the next day he is totally different and harms you. So it is very useful to use your judgment when you choose your friends, and I think it is wise not to trust blindly in anybody, not even in relatives. Maybe they are the most dangerous people who are next to us, because we don't really expect them to harm us or speak bad about us.

Nobody wants to be back-stabbed by a friend you ever trusted however other people are enjoying the fact of backstabbing or betraying their friends for some reason. That is actually a common problem in terms of friendship.

Nobody wants to be a friend with someone who says bad about you. Those are not friends. A friend should confront you first if they have something they don't like at you. Its for your own good anyway. But if they go to somebody and say something bad about you without any rebuke in the first place, then those people are not friends. You cannot trust anybody. Most people thinks that because they have the information they can use it for personal gain.