Democrats failed to knock Trump for almost everything he did which was dumb, during his whole Presidency. There was lots and lots of moaning about how cruel he was and how non-PC he was, but I think the only times he ever got flack for saying something dumb was when he suggested injecting bleach and that’s the sort of thing you can explain away as a brain fart.
I mean, you could have spent 4 years responding to every Republican with, “The guy who hired Omarosa? The guy who shrank his dad’s business?” Instead it was all, “He’s being mean to people who illegally entered the country! How dare he!”
If you don’t try a thing, you can’t say that it won’t work.
The primary mistake that the media always made was to treat Trump seriously. Other joke candidates were too dumb for them to even comment on. To the extent that they did, they’d just point to one example of stupidity, in a dismissive way, and move on. They didn’t for Trump because he’s just fun to watch, and they wanted all the clicks and views.
But the strategy of ignoring and dismissing is how you do it. Don’t even entertain the question. Mock and drop, that’s the way to win against nonsense, not to entertain it, debate it, nor take it seriously.
People don’t buy logical, well reasoned arguments, but they do read body language and adapt to match it. If the Democrats treat Trump like a serious person, whose thoughts and ideas should be given due merit - even if just to say that “most experts disagree” - then people will think that those ideas have value and that the experts are probably just crazy, ivory tower denizens that don’t understand things. No one would waste the time bringing up Trump’s ideas against them, after all, if those ideas didn’t have some merit to begin with. But, for whatever reason, we decided to go ahead and do it anyways.
I genuinely recommend to try being disdainful and mocking. You will get far more change than by trying to engage and sway through discussion. Treat the idiot like you would an idiot and your body language will sell more minds than your words.