I think this is a really good strategy. This is how you point out that an argument feels illogical without having to actually talk about logic (which ironically has always caused a big disconnect trying to talk to the self-purported "facts over feelings" crowd).
Not only that, the foundational pillar of authoritarianism is the desire to be "normal". That's why deviation is punished. Presenting it as give that they're deviating from the norm ought to have a chilling effect.
Short answer, it's not. It's effectively legal because the circle Venn Diagram of those who would roll coal and have Punisher/Back the Blue stickers on their trucks and absolutely zero enforcement, but it's TECHNICALLY illegal.
I got coal rolled or whatever. Hopped in my car and follow the fuck to the grocery store. Keyed the ever loving FUCK out of both sides of his truck, actually damaged my key a little. Big ass sine wave up and down both sides of the entire thing. Drove off laughing into the sunset.
"Weird." That's a perfectly succinct word to make anyone stop, actually reflect on what Trump and his cult are saying and asking themselves whether this is really what they want from their next leader.
It's not specifically charged at a specific physical characteristic of trump, Democrats dishing out a low blow for once yet unlike all of Trump's low blows.
Optimistic take: If Democrats could have just a single word be a silver bullet, "Weird" would be it. (No offense to weird Al, he's great and he can keep his weirdness)
Think about the next time Uncle Jack at the dinner table goes off on immigrants taking the jobs, America is a 3rd world country, we should ban books, ban calling people what they want to be called, climate change is a hoax, how terrible DEI wokeness is, making fun of Kamala etc., when no amount of arguing policy or morality is going to convince him otherwise. Just responding with "Weird.", might shut him up and make everyone at the table reflect.