I've been preaching the retardedness of gearscore since I became generally aware of its existence. I have two go-to reponses that I feel compelled to add whenever I see gearscore mentioned. The rational
"Y'know, I always say that it's a good thing bad players can't get good gear, or else gearscore would be practically meaningless"
or the equally valid
after which I will never allow any time for rebuttal before I swiftly conclude my argument with
I always say the best way to judge a player you haven’t yet played with is by looking at the parts of their character that the player does have direct control over, like gems and enchants and talent spec. I guarantee you that a crap player will make his lack of class knowledge blindingly obvious in his choices there.
And if you do need a clincher, look at his name. Does it contain his race, class or spec? Does it contain the words “leet”, “pwn”, “dps”, or all of the above? Bonus fail points for a Tauren who name contains an ingenious pun alluding to the hilarious fact that Taurens resemble cattle.