The factor you're missing is the potential for a criticism to advance the discussion. Everyone believes that they occupy the intellectual high ground, and that

The factor you're missing is the potential for a criticism to advance the discussion. Everyone believes that they occupy the intellectual high ground, and that it's everyone else who's guilty of confirmation bias and wooly thinking. Therefore, anybody else's accusations of confirmation bias and wooly thinking are merely a product of their own confirmation bias and wooly thinking, and can safely be ignored. Attacking the methodology mitigates this effect. By demonstrating that they spent serious time digging into it and trying to replicate it, the authors give a strong signal that they're not just exercising in armchair skepticism. This, in turn, lends rhetorical weight to their attack on the premise. Without it, it would be as easy to ignore, and as quickly forgotten, as your average comment on Hacker News.