Sarmatae1:

By your criteria we should not accept any premise that Hitchens has on evolution because he is not a biologist.

How is Hitchens at cladistics? Evo-devo?

Hitchens can be a secondary source. He can teach what he understands about evolution. But he can't be a primary source.

Hitchens is a well-educated person, and he might be able to spot a few problems in primary sources. But a lot will go over his head. Scientists who've fully mastered the relevant material are in the best position to review another scientist's work.

Shannon Brownlee's credentials in this area are really beyond reproach.

There are a few journalists in the habit of repeating disparaging canards about medicine*, usually followed by "therefore homeopathy," or the like. Shannon Brownlee is one of those, sadly.

Hey, I hate rich corporations as much as the next guy. Boo BigPharma! But Jesus H. Christ, please don't convince the public that everyone's opinion is just as good as all those pointy-headed scientists. We need the authority of a scientific consensus. It's the only weapon we've got against the uber-powerful who would love to ignore basic rules of evidence.
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*example: "...how many people are aware that LESS THAN FIFTY PERCENT (50%) of western medical practice is based on valid scientific evidence and some experts estimate that number is low as FIFTEEN PERCENT (15%)." Meh.