I'm not really sure if this is the right place to ask for help but whatever, it might help me sort through my thoughts. I've never had a problem like this before.

About a year ago, this friend Bob [m25] met up with me [f24] at a bar so we could catch up and chat. We were good friends back in high school but fell out of touch through out the years. I heard a rumor that he was dating my friend's sister, Julie. (We'll call the friend Amanda.) When I asked him about it, he went on a strange rant about how she broke up with him among other details I can't remember but couldn't really make sense of. 

The following weeks after I was told by Amanda that Bob raped Julie. As far as I know the police were not involved, hence no prosecution nor evidence collection. So it's really been reduced to his word against hers. I don't really know the full story, nor do I understand what really happened between the two. Now a year later, he wants to hang out and build up our friendship again. 

I don't want to continue the friendship because I feel as though it would show that I don't support Amanda and Julie and their family. BUT I don't want to have to say, "Look Bob, you're a rapist. I can't be seen with you." Since I don't know the whole story, I feel I would be the one "casting the first stone."

I'm a terrible liar and I'm bad at confrontation. What can I say to him that indicates I won't hang out with him but won't stir up trouble? 

EDIT:
user
Friend is a suspected rapist. Would like to not see him anymore without mentioning it's because of the situation.
assistant
I'm not really sure if this is the right place to ask for help but whatever, it might help me sort through my thoughts. I've never had a problem like this before.

About a year ago, this friend Bob [m25] met up with me [f24] at a bar so we could catch up and chat. We were good friends back in high school but fell out of touch through out the years. I heard a rumor that he was dating my friend's sister, Julie. (We'll call the friend Amanda.) When I asked him about it, he went on a strange rant about how she broke up with him among other details I can't remember but couldn't really make sense of. 

The following weeks after I was told by Amanda that Bob raped Julie. As far as I know the police were not involved, hence no prosecution nor evidence collection. So it's really been reduced to his word against hers. I don't really know the full story, nor do I understand what really happened between the two. Now a year later, he wants to hang out and build up our friendship again. 

I don't want to continue the friendship because I feel as though it would show that I don't support Amanda and Julie and their family. BUT I don't want to have to say, "Look Bob, you're a rapist. I can't be seen with you." Since I don't know the whole story, I feel I would be the one "casting the first stone."

I'm a terrible liar and I'm bad at confrontation. What can I say to him that indicates I won't hang out with him but won't stir up trouble? 

EDIT:
user
A friend of mine that I haven't spoken to in a while is a suspect of rape. I want to avoid
assistant