The rest of us are hearing this for the first time.

Not me, I grew up with one of those people and he was awful. And because he was the only Trekkie in the whole town, pretty much everyone I grew up with has a terrible opinion of star trek and its fans. I bet a lot of the negative perception of the show comes from people like that. People like that are not that common, but neither are outspoken star trek fans in general, so most people probably have a pretty equal chance of meeting either type of fan.