My mom had an affair and my parents are trying to work it out. On thanksgiving I want my boyfriend to pretend?

like nothing happened, be pleasant and talk with her some. She is in a fragile state right now so we are all trying to stay positive, especially for the holidays. My boyfriend is so enraged at her for cheating on my dad (they are very close) and also he has seen the hurt it has caused me. He feels like he cannot fake being nice to her and that I shouldn't even ask this of him. Am I wrong to ask him to pretend for a few hours on thanksgiving?