Should I be friendly to the person who got my friends in possible legal trouble?
What did they do to get themselves into legal trouble?
They stabbed some guy to death
It's okay to become friends with someone who reported a friend for doing something illegal. While loyalty is important, sometimes a friend can do something so bad that they don't deserve a second chance.
Should you be saying that?
I'm just trying to tell you that you don't need to keep in touch with someone so dangerous. It may hurt to let go of a friend, but would you want to be associated with a killer? It would be great to make a new friend instead with the one who reported them.