alt Hacker NewsQuestioning the person who made the claim, sure. Get them to elaborate. That improves the discussion. But halting discussion until they can come up with the words of someone else to justify their claim, as seen here, just makes you look stupid. If you would rather talk to someone else, go talk to someone else instead. At the end of the day, all is fair in discussion, so go for it – call for someone else to enter the discussion if you want. But as all is fair, we're also going to call out your stupidity when you do.
The bit that you're (intentionally?) missing is that this is just a polite way of saying "you're full of shit". The only person being stupid here is the person making strong empirical claims without qualifying them or providing supporting evidence.
I could see a reasonable complaint that asking for studies is being passive-aggressive, but it's the sort of passive-aggressive that both helps keep the discussion more civil and leaves room to actually substantiate the original claims (that is, it's actively better for keeping the discussion going!). Just saying "lol, no, wrong" kills the discussion far more than talking about (lack of) evidence.