[philh]

If someone writes something, it's "true" or "false" regardless of their political opinions.

On the other hand, someone's political opinions change what they're likely to write, so if you don't know whether it's "true" or not, knowing their political opinions can justifiably alter your beliefs about the text.

I think people tend to overweight the second consideration, and it seems particularly irrelevant in this case.

(Scare quotes because it's rarely as simple as true-or-false, e.g. "literally true but horribly misleading".)