JayUtah
Penultimate Amazing
It's not a Common Law jurisdiction BUT the general principles will probably be similar.
My post crossed with yours - my point simply put being that he has to a large extent made his own bed by raising his profile in a crazy arena.
Yes, I'm sorry, that was essentially my point. While Danish law undoubtedly differs from Common Law, I'm relying on the wisdom of the seminal tome The Law of Torts, which was written early enough to encompass not only English Common Law but the general legal theory of defamation throughout the civilized world.
As you say, Harrit has largely made his own bed and it is up to him now to lay in it. It is too late for him to adopt a false reputation as a respectable scientist free of harmful controversy.
Merely rendering a low opinion of someone does not generally defame him, except that under Danish law certain protected classes similar to those in the United States are entitled not to be defamed according to the properties of the protected class. However matters of pure opinion such as "fool" or "freak" would probably not be actionable.
While it is one possible defense against defamation to prove that the allegations made are true, it is not the best or only defense. As stated, opinions are generally not actionable because they are not allegations of fact. I may think you a fool and you may think me a fool and we may publish those opinions, but others are free to form their own opinions. Hence defamation does not generally arise. It arises from allegations of fact, that a reasonable person would be likely to believe and would serve to cause that reasonable person to form his own low opinion of me. To present my own judgment and ask you to accept it is not defamatory. To feed you false information that would entice you to judge inappropriately, is defamatory.
The question of truth is not whether Harrit's claims are true, but whether the defendant's claims (i.e., those in defamation) are true. As the product of the defendant's judgment, and not matters of objectively scrutable fact, they are inherently neither true nor false. Harrit's public statements may be perfectly true, but the plaintiff's judgment may not be swayed by them. Creationists call skeptics all manner of vile names and render all manner of public judgment against them, regardless of the truth of the skeptics' statements. So long as the Creationists merely render opinions and refrain from offering statements of putatively credible fact, they do not defame.

, but for some reason, Trump hasn't gone for it.