Bingo. This is the classic case of a tech geek looking at things through a lens of "abstract principle" when it's really not appropriate. Yes, sure, I think we can all agree that in a perfect world no one should get preferential treatment because of an objective fact of existence like ethnicity.

But in the real world, we have social groups with complicated dynamics. Expressing solidarity with your group is a normal and important part of this. Tech geeks do it too! And yes, sometimes that takes the form or a free beer or a "Greek discount" or whatever.

a bartender I once knew in a "late stage gentrification" neighborhood would feed me free drinks for listening to punk and not being a yuppie. Same subculture = discount

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?

Again, you're citing "right". I'm saying this is a case of complicated social interactions being benign in one case where the same kind of behavior would be discriminatory in others. You can make it right/wrong if you want to, but you're not going to solve anything by doing so.

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.

In what case is it benign?

Because writ small this sort of thing is isomorphic to "Let me buy you a beer." (see armenarmen's post above for a great example). That's a friendly gesture of kindness and common cause, and it makes friends. Those are good things, right? It's happens also true that these gestures are almost always offered within some social group or another. They're both "nice" and "exclusionary" at the same time. Isn't our world a funny place?

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?

But isn't that always going to be racist? Even in the case of DHH, honestly. A programmer meeting another programmer and doing favors for them that have nothing to do with programming?

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:)

Actually, think very hard about what you're proposing. OK, let's propose a humanity where there is absolutely no group cohesion whatsoever. What's the result?

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.

Because there is a higher chance that I will enjoy a conversation with someone I share some background with. Call it an easy icebreaker.

Edit: Added 'easy'

Different treatment alone isn't enough to make something problematic, it's when the discrimination serves to perpetuate some sort of broader injustice that it becomes a problem. Discrimination without systemic injustice is just harmless capriciousness.

In that context, no. If it was an everyday thing like in the original context, it's a different issue. A better example would be to look at how expat anglos operate in different countries - "if you were living long-term in Hong Kong, would you feel uncomfortable with a fellow [nationality] giving you a discount because you were of the same group?"