They say "fricking" instead of actually swearing. They probably have ketchup with every meal. Two Big Bang Theory fans I know genuinely own shoes which fasten with velcro. The word 'basic' is a bit of a cruel insult to throw around willy-nilly - we can't all listen to Mac DeMarco while munching gourmet scotch eggs - but they do tend to be united by a complete lack of imagination and cultural adventurousness.
It's not just the fact that liking Big Bang Theory indicates a total lack of taste, it's the vague sense that they feel that liking it is a big shiny gold badge of honour which indicates that they're intellectually superior to fans of other sitcoms. As we've already established, The Big Bang Theory is not a clever programme. It's that middle of the road that if you swapped their references to Star Wars and astrophysics for references to forests and body hair you could be watching Harry & the Hendersons.
If you want intellectual jokes, go and watch Rosencrantz And Guildenstern Are Dead or something. You'll not find them on Big Bang Theory, so drop the cleverer-than-thou attitude guys.