Use this template if somebody comes onto a talk page and their entire comment amounts to: "RationalWiki doesn't believe in [Pet Theory], but [Pet Theory] is rational, so RationalWiki shouldn't be called RATIONALWiki."
Do NOT use this template if somebody comes onto a talk page with (1) a specific complaint about the article or (2) evidence (good or bad) for [Pet Theory]. Being rational requires constructively engaging other people, even those with (an) idea(s) you consider to be irrational, in order to determine whether or not their idea(s) are actually irrational. Placing this snarky template does not engage anyone in dialogue and makes RationalWiki seem aggressive to alternative ideas.
If you really want to place this template, but their comment actually has some content to it, maybe try placing the template and engaging them.