advice on pervert brother in-law

I slept over my sisters house last week while she was at work to help babysit while her husband would run errands. While I was over there my brother in law who I've know very closely since I was 8 (I'm 17 now)  had started asking me perverted questions such as if I knew what a vibrator was.. I froze I didn't know how to respond because I felt so uncomfortable I wanted to cry because I was scared of what was going to happen next tbh... I told him "I don't think you should be asking me those questions" he said "what? I was talking about the vibrator on your phone when someone calls." Also that day my sister accidentally took his credit card and he didn't have a lot of money left and we were an hour away from my home(my sister lives on a farm, I live in the suburbs) he said he had $25 and I said he should be fine and he said he has to buy the kids food and stuff and basically he said to me "jokingly" that somebody is going to have to sell some ass .. and he said they wouldn't him or the kids and I felt so uncomfortable and finally he took me home . I told my mom about it and she said all men are perverts and that to just not goto her house anymore alone with him and to not tell my sister. but I told my counselor about it and I wanted to tell my sister because what he is doing is wrong and so I gathered all the courage in me and told her  and she was super upset that he did that and she was disgusted with him and she was glad I told her because it was the right thing to do and she told me she is going to confront him when she is calm and has thought about it. I told my mom that I told my sister about what he said and my mom says that I'm in the wrong and that I shouldve told her(my mom) to tell him to stop and that I shouldn't have told my sister n that I could be the reason why they divorce n that those things hurt people when they find out their loved ones did that but my brother in-law has told me things like that in the past about  a year ago(he's told me after I finish taking care of the kids that I can take care of him after) and I told my mom and she didn't do anything. I GOT SO PIST WITH MY MOM and I told her I'm not in the wrong for telling my sister what her husband has been doing to her little sister and that my brother in law is a grown ass man (he's 34)  who shouldn't be doing those things and I don't care if it hurts my sister or her marriage I'm not the reason they divorce, it's her fucking perverted husband who ruined the marriage. I just feel bad because my mom is angry with me that I told her and I told my mom she is stupid for saying I'm in the wrong  (I'm sorry this is long but I just need reassurance that what I did wasn't wrong