Tim, the ad revenue is a red herring. If all of these social media companies would just say "This is America. Free speech is paramount and we're not going to censor anything that is not illegal." the advertisers would STILL advertise on these platforms. The reason? Because that's where the consumer's eyes are.
What has the advertisers jittery is PRECISELY the fact that these social media companies ARE censoring, so the advertisers feel they have to bend the knee. If the social's didn't bend the knee, then the SJWs couldn't target the advertisers.