kaguraTPJ: We all have one of those in our families. Two in mine. Fortunately, it wasn't my father.
If your boyfriend knows his dad is an ass, which he probably does, then this is something you and he can probably deal with. I gather your boyfriend is fairly young, but as he becomes more independent, this will become less of an issue. He will see his dad only as often as he has to and will take you to family events only when necessary. I have some close (biologically) family members I see only when absolutely necessary, about twice a year. I figure I can handle anything for that length of time. If you really like this guy, this is a good opportunity to be a big person and just smile and nod when dad is being an ass.
If you boyfriend is clueless about dad's behavior, then you have a major problem. Probably better to run while you can.