Redhat dose some questionable stuff, especially all that union busting bs but it’s far from the worse employer and if you love foss you probably do something you love there.
I agree, I am certain that there are thousands of great and passionate about FOSS people there. I’m just not that certain about IBM ;) It’s still probably better place to work at than most.
All in all, I am only saying that the fact that somebody cites “personal reasons” doesn’t mean there are no other factors at play.