I kind of agree. The kid's 22. There's no way he knew him mom was dead. I think it was just a innocent but stupid "I banged your mom" level joke (have these ever been funny?) that was said to the wrong person.
Not defending his actions obviously and hopefully he learns a valuable lesson out of this but the lifetime ban from all ballparks might be a little much.
Edit: I feel like fans have said worse and players have heard worse.