Individual teams have rules, some very strict. The league does not have a rule, AFAIK.
MLB is 25% foreign-born than with very few from Mexico, and is less than 10% American black. Players generally spend minimum time in college. America-hate is not normal among MLB players.
Disrespecting the anthem has happened in MLB, but not for overtly political reasons. Players and teams call out offenders.
A lot of players are from the Dominican Republic. They are grateful for getting the opportunity to play, and from what I’ve seen, most of them are good people.
I dare say it’s had to find anyone in sports more class these days than the Rangers’ Adrian Beltre.
It’s 162 games per season. There will be a spot sometime that doesn’t hurt the team’s record for a pitcher to express his opinion of kneeling during the anthem. No other sport has this dynamic. It is why we don’t have celebration dances down to first base after drawing an important walk or elaborate chest slapping displays after making a routine play to get an out at first, where you have this garbage in NFL and NBA. No one likes getting stuck with 90+ mph in the ribs.
Freegards