Public debate about banning on political ads on Twitter vs. not on Facebook has gone fully off the rails. Both Dorsey and Zuckerberg are wrong about it, but--counter intuitively--Zuckerberg has it less wrong than Dorsey.
Where Zuckerberg's instincts are kinda right is I think he recognizes on some level that when one company has control over like 90% of a media market and can make decisions about what speech is or isn't allowed, we might want to consider applying 1st amendment protections.
Yes, there is a "bUt pRiVaTe pLaTfOrMs aRe eXeMpT fRoM tHe FiRsT aMeNdMeNt oBLiGaToRy xKcD https://xkcd.com/1357" trope. Spare me.
Companies with monopolies are effectively the same thing as governments because they replace government as the de facto public square.
As such, speech on such platforms should either be subject to 1st amendment protections, or the company should be broken up into federated platforms that set their own speech rules. Zuckerberg seems to prefer the former. We should prefer the latter.
The root of the problem is Facebook's/Twitter's monopoly, not political advertising. Break up Facebook/Twitter into a bunch of independently-owned, federated services (e.g. Diaspora / Mastodon) that each set their own speech rules.
TL;DR:
Dorsey: Preserve my monopoly and I want to censor things on it with impunity.
Zuck: Preserve my monopoly but I'm skeptical of censorship.
What we should actually want: No monopolies, so the question of regulating speech on these platforms is fully moot.