I dont think there is much of a stigma. Even in other places. I live in switzerland and sometimes listen to german rap. Even they think it's cool to rap about dragon ball stuff. And we all know rappers are usually the first to label something like anime as lame. And they do actually. I can remember bars where they say it as an insult. But in the next song they have dragon ball bars. It's not a single rapper doing it either. I've heard multiple. I even know one that has an album called genkidama, which is what the spirit bomb is called in our dubs.It's one thing to like Dragon Ball when everyone watched it on TV when they were younger, but it's definitely a different story if you still watch it. In the best case people will accept watching one of the new movies for "nostalgia", but they don't consider it to be as acceptable as a current active interest of an adult a lot of times.
Or at least that's how it is in my country, where I would argue DBZ was even more popular than in the US.