Don't unless you want to join them.

If they're a friend, help them.

If they're not, stay away.

Interfering with a disciplinary process like that will just get you fired, especially so if you were wrong with your "fact".

(P.S. I have represented several colleagues-who-were-friends in official HR meetings where we were "against" our employer and I decided to get involved even when I could have just stayed out of it. But you have to be fucking careful and - like me - you have to know that you can screw them to the wall by *following the rules*, and be principled enough to say "Fuck it, I don't care if they sack me for doing this, it's the right thing to do").