The guy should have started a movement, or a group, using the points from the guest speaker on why they shouldn't have had that speaker, etc etc... This organization of people holds more weight than an individual. This is the way.
Almost every state now has at-will employment laws. The company doesn't need a reason to get rid of you.
Being "polite" is nice if the person you're talking to is also nice. If the guy wanted to bring attention to the fact he did it very well.
What US-backed Israel is doing is utterly abhorrent, and protesting makes sense; I can understand why an employee wouldn't want to aid them in any way - but with oil and gas off the coast of Northern Gaza, the US about to build a port for it, and the US, UK, France and Germany govs supporting Israel to the hilt, real sanctions are not going to happen. Hell, the west is still supplying Israel with weapons, and Israel hasn't even been kicked out of EuroVision!
But... one person disrupting a meeting will have limited effect, and is guaranteed to result in a firing.
IMO a better plan would have been a petition, signed by as many employees as possible. Failing that, looking at strike action through union(s) could be a good idea. A single employee has very little power - but if a significant number banded together, their power is much greater.
Any means of generating substantive resonance within an org is jealously reserved by those at the top of an organizational hierarchy.
It's a Catch-22, but part of Activist 101. If you aren't drawing ire, getting retaliated against, or getting surveilled by someone, odds are you aren't being a terribly effective Activist.
Which is why we all continue to support our corporate overlords.