Just for some German context: the Nazi salute is not covered by any freedom of expression or opinion in a political context. What Elon did on stage would have landed him in a German court. Similar restrictions apply to displaying certain symbols, e.g. the swastika. German cops are legally required to intervene when they see them in public.

I don’t know the video in question, I don’t know if the cops overreacted - a reaction was required though.