Pay attention to the music and the crowd reaction in the background of that scene. There is nothing joyful about that scene. It's actually very sinister. If anyone gets any joy or inspiration from that, that says more about them than the film. Can't fault the filmmakers for some idiot misinterpreting their work.
This is a very naive way to look at the movie. Or any movie. Just saw the clip, and it's great acting, but I can totally see some incel or alt-righter glorifying it. They (director, writers of the movie) don't make De NIro's character go very far in the counter-argument.
Obviously, we all need to see the movie first, not just a clip from the one of the movie's the most shocking moments. But, like someone else says, nobody should handwave away the concern that too many people might glorify the Joker as an anti-hero. It's not so much that well-minded or "smart" people aren't going to pick up on the "music and crowd reaction" nuances of that scene, like you say, but that people already susceptible to these types of glorifying images are going to horribly misinterpret the movie, if the movie is even bothering to avoid such misinterpretations.
It's precisely the type of misinterpretation of a movie we don't need right now. The worse of times for it. For the sake of the movie, the actors involved (a lot of who I admire a lot), the director, Warner Bros, and others, I hope the movie manages to pull this off, because if it doesn't, it does more harm than any good.
