It is absolutely prejudicial. Citing a case where I benefit from it doesn't make it right. Why not randomly give a beer to every 1000th patron, or every 10th shirt with lettering, as a conversation-starter?
And, it must be noted: if you really think hard about things (something that tech geeks, in my experience, are really bad at doing in a social context), you'll realize that your "wrong" filter always seems to be applied against some group other than the ones you're part of. Whether you realize it or not you participate in this kind of social game too, even to the exclusion of other groups. And it's not "wrong" when you do it either.
Basically you don't like "Greek discount" because you're not Greek. But if you met DHH at a bar and he offered that beer, you'd take it, right?
I don't really think that I would feel the urge to offer someone a beer because I was aware of them as a programmer - but if they went to my high school? I don't think so, and I can't recall doing that, but I just might be misremembering. Would I take it? Of course, I like free stuff. I don't know if I'd offer it. That feels like a weird backslapping "this guy is alright, he listens to Black Flag" or "he's from Arkansas, woo pig!"
Of course, if I used rails, I would offer him a beer, but that's because I'd be showing up at the bar after a day of making a living off of his work:)
It certainly doesn't look much like the world you're familiar with.
If you look around, there are plenty of species that work that way. You really shouldn't have to imagine that hard.
I often amuse myself when the recurring gender debate (or other similar debates) come up on HN by trying to convince participants to first concretely describe the world they are actually trying to produce before they go too far off into la-la land making wild prescriptions about what needs to happen. This is another example of that sort of thing. Are you sure you want to produce a world in which nobody, ever, for any reason, has any sort of preference for one person over another and gives any sort of preferential treatment as a result? If you really think about it, probably not. Trying to take the ultimate hard line on "no discrimination" isn't a sound solution. It is neither logically nor socially viable. The method has become mistaken for the cause itself, the direction for the destination.
Edit: Added 'easy'