Very much agree with you on this point. I think he should keep his political opinions to himself, but he shouldn't fired.
Now about the "Let's go Brandon." I think it is a funny poke at people who had no problem with Robert DeNiro yelling "Fuck Trump" or Samatha Bee calling Ivanka Trump a cunt. Personally, I think all the Trumps are lying, cheating, fraudulent tax cheat grifters, but FFS what is good for the goose is good for the gander.
If it is OK, even cheered by MSM for people to curse out Trump and his low IQ family for 4 years, well then "Let's go Brandon" is fine by me. I mean, "Fuck Joe Biden" is also OK, but I find the trolling aspect of "Let's go Brandon" just a hilarious comeuppance.