Public Figure=/=Politican for starters. Celebrities are public figures. While I'm sure you could find SOMEONE I imagine the number of parents who would object to you having their child write any of the following is somewhere between nil and none.
Elon Musk, Stephen Hawking, Neil DeGrasse Tyson, Bill Gates, Steven Spielberg, Peter Jackson, or Steven King.
I could probably make a fairly long list of celebrities that hardly anybody has any emotional response to. I mean does anybody hate Elijah Wood or Matt Damon? I'm not asking do you love them but is there anything about them sufficiently controversial that people would freak if you wrote to them? The worst thing about Shaq is he tried to act for a few years, professional B-ball player, volunteer cop, what's not to like? I suppose there are some hyper religious people who might object to Joss Whedon (creator of Buffy the Vampire Slayer, director of Avengers) I mean vampires! Other Gods!
So in short yes, there are fairly non-controversial people.
But every single one of them could start making enemies just by speaking publicly about politics. That's where America is right now.