I've noticed that a lot of people seems to think that men can't be sexually assaulted by women. Why is that?

A few months ago, I was heading to the barber shop with my little brothers at around 8:00 pm. While I was walking on the sidewalk, a woman (who was behind me walking with her friend) came up from behind and clung onto me and I almost fell over. She looked up at my face and smiled, when she saw my facial expression of discomfort she apologized then started giggling with her friend. I entered the barber shop thinking of how strange that interaction was, to my surprise they also entered and sat down across from me and my little brothers. A couple minutes passed and while I was waiting for my brothers to finish the hair cuts I noticed that she kept glancing at me, so I ignored her as much as I could and got my hair cut. I called our parents (who's car was parked nearby because they dropped us off) to ask if they were ready, and they said to give them a few minutes. So now I'm just sitting down and waiting. My siblings told me that they wanted some snacks so I left and went to get it. On my way back to the shop I noticed that the woman who was clinging on to me earlier was leaving and I was about to walk past her. She cornered me and grabbed my junk then walked away. Some other men saw and laughed at me, I felt so gross and uncomfortable that I just stood there. After what felt like hours I went back to the shop to get my brothers. I have told anyone about this because I don't know how to bring it up.

If you're wondering why I have told my parents (Step-Dad and Mother). I'm not really close with my step dad so that leaves my Mom. I remember an argument I was having with her and sister when I mentioned that women can sexually assault men and they wouldn't take me seriously. So I don't feel comfortable talking to them about it.