I have learned to keep my mouth shut tight about my adult kids significant others and to get along with them, whether I liked them or not. It is often a dealbreaker with our kids if we talk smack about whom they love, even if we feel we have a good point. In fact I am agreeable and accepting of their adult choices. You have good reason not to like him, but right now telling your daughter wont help her and is hurting you.
Adult children usually like validation and praise insted of our opinions. I learned this from my angel of a mother in law. Unless my grown kids ask for my opinion, if I cant think of anything nice to say, I dont say it. I cant always refrain myself in all aspects of life lol but I do with my children.
Maybr mellow out on the boyfriend. You picked your partners, good or bad, and now its your daughters turn. Especially regarding grandchildren it is best to be on good terms with the father. Sometimes you cant but you can try.
Unless so is beating your daughter or the kids, I would stop bashing your daughters boyfriend. He will either shape up or your daughter will figure out on her own that he is a creep.
I know its hard to bite our tongues. We are mothers. But our grown children are adults too and may prefer your role turn in supportive best friend rather than advisor.
This is jmo. I hope I did not offend you as I did not mean to. Also we are just other parents so take what you like and leave the rest.