Hey one of my friend’s FIL has an autistic child, a soon to be MIL is a Scientologist and telling him autism is imaginary, and he is staring to believe it.
What should I do to educate him on the dangers of Scientology before it’s too late?

Any good articles that lay out how they operate and destroy lives?

Not an article, but a book from David Miscavige's niece herself and her escape from Scientology. It's pretty damning expose of what goes on behind the scenes from someone who grew up in it.

[www.goodreads.com]

and of course for video there is the documentary Going Clear and the book that inspired it, though I have not read the book.

Good luck in your fight.