I think in some ways you are understating the case against steel manning here because even well-intended non-bigoted people frequently hold their uncontroversial not at all hateful sounding (and even sometimes factually correct!) opinions for very confused reasons, and some of the same points about predictive failure if you steelman them presumably apply in those cases too. It’s not just bigots who have poorly justified views. (Obviously there are distinctive costs to steelmaning bigots that don’t apply in other cases.)