Is it wrong that my former step son comes over?

My step son is 18 almost 19. I had been in his life since he was 3. His mom is "in" his life but they aren't close and don't have much of a relationship because she's very narcissistic. Me and my ex husband divorced last year after my step son went to college. My ex let me keep the house because he was moving out of state to be with someone he had an emotional affair with. My step son's university is in the same town. He isn't close with his biological mom. My husband moved so I'm the only family he has down here. He does call me mom and will come by on a regular basis to do laundry. I've been with my boyfriend for 5 months and he knew my step son was in my life and he always will be. He acted okay with it. I never did anything with my step sons room and for the last couple weekends he's been spending the night at my house in his room because his college has been having some protests and the university has been having the police department there to keep the protest under control. The police in our town are POS. There has been so much police brutality going on at his university that it's ridiculous. My step son would send me videos of the things they were doing and throwing people down who aren't even a part of the protest. I think the police in our town are just bored and thought beating up college students would be fun. So to get away from all the nonsense he comes up on weekends. Especially since his room is still there..my boyfriend doesn't like that because he finds it disrespectful to have another man in my house. This man is a teenager and I've been a mom to him since he was little. I think he's being absolutely ridiculous. I know people say when the marriage ends so does the relationship with children but I don't believe that. Especially if you've been in their son as long as they could remember.