The "genocide Joe" crowd are, for the most part, well aware that Trump is just as bad for Gaza as Joe is. They're not arguing for supporting Trump, they're arguing that both choices are bad.
This is not a rational position, obviously, because if you care about protecting Palestine you're still better off supporting the Dems to avoid the worse option of Trump, but for a lot of people it's hard to stomach the idea of voting for a murderer, no matter what the justification is. The not entirely unreasonable argument is that voting for the Dems to avoid the worse option basically encourages the Dems to be more shitty because they know they can always throw the threat of the GOP in everyone's faces when they're called out. I don't agree with this argument, but I see how it's compelling to people.
They're not Trump supporters - at least, not intentionally - they're just sick of the whole dicochtomy of being asked to choose between bad and worse. I can understand their frustration, even if I don't agree with the choice they're making.
I mean, Hulk isn't exactly a d-lister. The guy still gets huge pops at wrestling shows. It's more that he's absolutely trashed his rep with younger people by constantly being a disgusting piece of shit.