In other words, he publicly harassed a colleague who (for what could be any number of perfectly valid reasons) preferred not to publicly state their beliefs. That would seem to me to be an eminently reasonable reason to fire someone. If you go around publicly harassing your colleagues to publicly state their political opinions, you deserve to be fired.
“Thanks for letting me know how you feel about this, I consider this a valuable opinion and think deeply on it”.
Then go ahead and do whatever you were going to do anyway, but at least let them know you’ve heard and acknowledged what they had to say. Sometimes folks just want to be acknowledged, that doesn’t seem like too much of a burden.
Edit: this is very basic EQ and active listening, not sure why it's controversial to have good social skills.