Hamilton doesn't "yell" "or else". He just wants a selfless act of showing unity on an issue. Drivers are obviously free to say no to that, but Hamilton is also free to call them out on it for choosing to not do it. Personally I call bs on the "I want to focus on the race" excuse. There are many formal stuff that takes places before every damn sport event, including races. Would anyone be fine with someone saying before a world cup match "sorry guys, I will skip the anthems because I want to focus on the match"? Or the same for the Indy500: "sorry guys, I am not an American, I won't stand up for their anthem, I want to focus".
I have no idea wtf Leclerc is thinking with that statement. It reads like he doesn't want to do it because it would hurt the feelings of some people (aka. racist). The only people who would see that formal gesture as controversial are racists.