OT: Anti-Gravity & Monty Hall

Given the group now prefers OT subjects to metalworking here is something for you to use the brain power on:

A pal of mine, who is not a professional physicist is challenging existing views of Dark Matter and proposing Anti-Gravity Matter as a better fit with observations of the universe. He has many detractors, but if you remember the solution to the Monty Hall problem as proposed by Marilyn Vos Savant was decried by over 1000 PhD's in Mathematics and relevant sciences and they were wrong. I suspect snobbery had something to do with it as the article was published in Parade magazine rather than a professional journal.

Wiki always has a view:

So guys, the challenge is this - using the brain power of the metalworker who has a lifetime experience of daily problem solving can you take a look at this and decide if the professional view is just establishment and wrong or if here is a happy amateur who has latched onto something in his garden shed that has real merit?