"You can't convince anyone of anything using rational argument" is one of those cached thoughts that makes you sound cool and mature but isn't actually true. Rational argument works a hell of a lot worse than smart people think it does, but it works in certain contexts and with certain people enough of the time that it's worth trying sometimes. Even normal people are swayed by facts from time to time.
In 2004, Michael Vassar gave the following talk about how humans can reduce existential risk, titled Memes and Rational Decisions, to some transhumanists. It is well-written and gives actionable advice, much of which is unfamiliar to the contemporary Less Wrong zeitgeist.