Hard to believe that your boyfriend could be unaware of his parents' attitudes, even after seeing them on display in how they talked to you. You're right--they would have been a problem, but his denial and defensiveness of them would have been a bigger problem.
I was more fortunate. When I introduced my West Indian fiancee to my family, they were not only gracious but genuinely welcoming, and through our 25 years together they made it clear that they were proud of her and of our children.
Thank you for sharing your story.