My guess is that they misunderstood what he said. Who would say that among a group of parents, even if it was a joke?
JFC I hope you're right, otherwise I'm not sure how I'd be able to handle this situation.
I would hope so too, but honestly I don't think it's possible to mis-hear that, given the exchange. ("Am I straight?" "If she was, I bet she'd #### me.") You'd like to give the other dad the benefit of the doubt and assume he's not a completely vile POS, but I can't construct anything innocent in this context that could have been mis-heard as what the OP wrote.
Not sure what I'd do. I want to say that my daughter never goes anywhere near this guy ever again and probably nowhere near any of the other dads who were sitting there listening, but I'm not sure how to accomplish that without socially ostracizing my daughter and thereby making things even worse. Good luck, OP.