Rush handled it artfully. He told his audience that the advertisers didn’t want the audience anymore. Now they don’t have them. You are right that future advertisers will keep this fiasco of bad PR in mind.
Which, IMO, is the main reason Rush said no to the advertisers who wanted to return. It's not about revenge, it's about telling future advertisers what will happen if they try to pull the same childish crap. Companies may now take a breath and think things over rather than have a kneejerk reaction to leftist propaganda.