Perhaps interesting here is that some of the things he said were definitely not defensible via "truth is an affirmative defense." But it's ultimately up to the jury, and they can also find him innocent because a reasonable person wouldn't be offended by outlandish accusations.
(Ultimately, though, they can find him innocent for any reason. If they decided he should walk because you can't legally offend cops, that's fine too.)
Truth is far from the only defense.
Opinion is not defamatory. Satire is not defamatory.
With public officials like police, even false factual statements are not defamatory unless you knew they were false and lied about it specifically to hurt them.