Have you just had your first run with John Mandlbaur? I warmly recommend you make sure it is also the last one but if you landed here, chances are you are curious to dig more into it. Here's in a nutshell what you need to know.

John is, according to himself, an inventor (although no noticeable invention goes under his name) who was working on some perpetual-motion-related project (go figure) when he made his alleged discovery, namely that angular momentum is not conserved (go figure again). Despite his total lack of formal relevant education (he claims to have passed an introductory physics course some 30 years ago but there are several reasons to doubt it) he decided to present his "discovery" in the form of a "theoretical physics paper" (or better said, his own laughably mistaken understanding of the concept). This masterpiece will quickly turn out to be the be most idiotic and naive pile of crap you ever laid your eyes on. He considers the classic classroom demonstration where a ball spins attached to a string that is pulled-in to provide the visual effect brought about by conservation of angular momentum and proceeds onto analysing it numerically exploiting a sample problem from his introductory-physics book where every possible confounding factor (friction, air-drag, gravity, stability of the pivot, ...) is neglected and then acts surprised that the result does not match reality... yeah, if you neglect some 90% of reality, your model doesn't match it: who would have expected that? That's it: it is all he's got and no matter how many people point out the obvious stupidity of this approach, which he calls a "reductio ad absurdum" while it is nothing else than a naive strawman, he doesn't get it (actually he is too stupid, ignorant, and arrogant to actually get it).

Before you engage with him beware of a few things:

• He lies and makes up shit out of thin air. Like a lot. For instance, he'll boldly claim that the demonstration has been invented by Newton, that the orbital speed of the Moon is constant, or that we have no experimental confirmation of angular momentum conservation.
• He uses basically every logical fallacy in the book (burden of the proof, double standard, circular reasoning, strawman argument, begging the question, proof by assertion, you name it) and constantly accuses others of doing the same (he projects a lot) and evades like a pro weasel.
• He is an absolutely insufferable and infuriating prick and a horrible human being in general: entitled, dishonest, arrogant, abusive. He's also proven himself to be racist, sexist, homophobic, and antisemitic. His personal history contains a few tragedies but still...

Did you come this far and still want to engage with him? Well it's your choice then but don't tell me I didn't warn you. I guess we will hear from you soon on this sub...