I'm aware of the origins of "Let's Go Brandon" and I was indeed making a joke, but ironically I kinda think "eff Joe Biden" is a less offensive statement than the slogan they've morphed it into. Because it's their slogan, and implies endorsement for everything they stand for. In much the same way they're not entirely wrong to claim that "Black Lives Matter" has gone from being just a statement of fact to an implied endorsement of the problematic organization by that name.
Also Brandon Brown himself used it to launch a cryptocoin scam, so there's that.
But yes, as regards the moral standing of my neighbors, it's still a big step up if it indeed represents a repudiation of the lie it replaced.