Here's a quick thought experiment: Suppose I create a small movie company based on another character also in the public domain, and I successfully receive a trademark for my logo, which is... Jesus Christ.

Does/Should that give me control over anyone selling or distributing other books, movies, pictures, and songs depicting Jesus?

In a sane world, the answer is "heck no", because trademarks are really about stopping fraud, where someone else is trying to leech off my good reputation by confusing people into doing business with them instead.

Now, one might plausibly argue that Jesus is "generic" and thus the original trademark was wrongly granted, but the same principles apply even if I rebrand under just one of the less-popular characters or symbols. ("As the owner Pontius Pilate Productions, your story violates my trademark!")

If this was a case that Morgan and Morgan expected to win they would not have withdrawn the ad.

That they did indicates that they don't even believe their own claims.

Mickey is still a trademark of the Disney corporation.

You're right though. This is an open and shut case that Morgan and Morgan will lose. There's only several decades of case law on this...

In both cases the company has zero rights to the underlying public thing, and the court just needs to ask: "Is someone trying to trick consumers into mis-identifying the company or product?"

P.S.: Even if the company transitioned into being a seller of commemorative Statue of Liberty figurines, their trademarked logo shouldn't give them the ability to monopolize the subject matter. In that other context it might even be revoked as too-generic and unenforceable.

It is strictly regulated how much money Morgan and Morgan can get out of someone who they represent.