What to do if you do not like your best friends boyfriend?

I met my friends boyfriend for the first time last week. I usually give anyone a chance but after spending a few days with him he is not a nice guy. Now she is upset with me. He controls her, acts like he owns her, he yelled at her in front of all of her friends, grabbed her arms really hard, he even lifted her dress up at a bar and showed everything just because he thought it was funny. He yells at me and is very mean to me and she doesnt defend me.. she will just say stop picking on her and he still does it. She is blind sided by him.. What do i say to her? I dont want to ruin our friendship but her parents would be mortified if they knew the type of guy she was with.