It's hard to see any coherent goal behind this behavior. There's no way this could be thought to convert anyone. It's most similar to a pep rally before a football game, where the goal is to whip up enthusiasm in your team's fans. The goal of a pep rally isn't to persuade the other team's fans to change allegiance; if anything, they just root harder for their own team, meaning in this case it will increase commitment among any Democrats watching.

The only possible thinking behind this must be, like the Trump rallies, to try to draw independent voters via an Appeal to Popularity; seeming to have more people on your side than the other team does. That's why Trump makes such a big deal about crowd numbers and insists on holding superspreader rallies despite the obvious health hazard; psychologically, people want to be on the winning team, and he's gambling that looking like more people are on his side will sway the uncommitted. But the way they're going about it is just so loathsome that the only voters it will attract are likely to already be voting Trump anyway. And independents who are still thinking things over may be driven away by this kind of boorishness.