How can I support her choices?

My mom is giving up her dream house because my stepdad has decided he wants to own property and wants his own garage, he hates doing yardwork and he doesn’t know how to work on cars so I don’t understand why he needs a garage, but to keep him from bitching about all of the stuff she owns (it’s apparently preventing him from all of his garage dream projects), she is going to give up the shit loads of money she has invested into making their current house exactly the way she wants it, and it’s all mostly because she doesn’t know how to tell him “No”.
She expects me to support her decision but how can I support something that is making me lose all respect for her?