The 'Fan Code of Conduct'
Does that override the 1st amendment?
Does a leasee have the right to be judge jury & executioner in a public facility?
MLB, BTW, has no right or power to ban the kid, legally.
It's

relevant what was said. If it was something that qualifies as "hate speech" I'd listen to the argument, but if the kid just yelled
"Hey your mom is a shitty driver" or "Your Mom gives terrible road head" or something like that, then this is completely an over reaction on CWS & MLB and the kud should sue them both for substantial damages.