I have a crush on someone I shouldn't have a crush on.
What makes them so dangerous to have feelings for?
Because he is already in a relationship.
That's too bad. It's okay for you to have a crush on the person as long as you don't do anything about it.
I know, but I just like hanging out with my crush.
Maybe you should avoid hanging out with him while he is in a relationship. It is fine to have feelings for him, but you should not act on those feelings if you know that it is wrong to have them.