Vent about MIL

My husbands father died when he was 18 so 10 years ago, well she has had a new bf for 9 years they’ve live together and she’s trying to have him called “grandpa” my husband is not close to him he’s barely even close to his own son and she forces him on us. I do NOT not want him being called that and I Honestly don’t even like him he’s obnoxious and calls people “loser” and “stupid” to their face as his disgusting way of joking and don’t even want my child around him. Has anyone dealt with this? I don’t want to cause a big fight but he’s not getting called grandpa and i can already tell she’s not going to respect our parental wishes 😒