I got sucked into a rabbit hole of make believe physics yesterday and I don't intend on doing this again today. Let him figure out himself how silly it looks thinking that it's "okay and legal to elbow players in the head when they try to avoid contact".
To give you an analogy, I was always a geography buff and started out very young reading encyclopedias trying to memorize borders and flags. So one day, as a 10 or so year old mind you, I thought I could hang with adults as they were talking about geopolitics, I think it was when they were in talks about creating the European Union, after the wall came down.
When I heard that they were talking about Sweden, Norway, Denmark and Finland it sort of confused me because I thought I had read in an Atlas that those countries are "Scandinavian" countries, so I in my infinite and very infantile wisdom proclaim that those countries could never be part of the EU because they form Scandinavia. They looked and smiled at me and I was so proud to have contributed something to an adult conversation.
Well needless to say it was pretty embarrassing to find out how silly it made me look and that's what you need to aim for here, let them talk, let them be wrong, let them think they are correct. Eventually, one day they'll come around and feel the shame... or they'll continue to look silly... either way, you can't win nor lose conversations like this, so it's best to just stay out of it.