I notice the 20yo boyfriend has a Hispanic last name. We don't know the girlfriend's ethnicity, but if she, her mom, and mom's boyfriend are not Hispanic, I wouldn't be surprised if mom's boyfriend is more upset about the question of race than anything else. It seems that when race gets involved, sometimes people will see things going on that aren't actually going on, if you know what I mean - and what's more, they'll be 100% convinced of it.

Now, if you couple that with jealousy, you get a really explosive mixture.