On one hand you're right, ad hominem filtering on the basis of demography is self-limiting.

On the other, it's ironic because the author is a specifically controversial character: https://rationalwiki.org/wiki/Michael_Shermer#Accusations_of...

I didn't say to ignore his "valid points." I intentionally didn't mention the content. I was trying to point out that, if, as you read the piece, you correctly inferred metadata about the author, (a) it's funny because (b) it means there might be more to the theories he is dissmissing out of hand.