Tell your friend it's nice to dream. Dreams are fun. But if everyone were in the same league, we wouldn't use sports--a method of sorting and judging people by their physical characteristics--as our primary metaphor for dating.
I mean, that's nature, right? Animals don't pair off so as to avoid hurting the uglier or weaker animals' feelings; they fight each other with their horns, spread their tail feathers, and bone the most attractive mate they can possibly snag. In its own way, human dating is just as competitive, and as brutal.
The fact that "leagues" exist as a dating concept so prevalently makes them real just by common agreement. Some people believe themselves to be above dating certain types, and so they are (because they don''t date those people, because of their belief that they shouldn't).
They believe it, so it's true. It's like a Field of Dreams thing, but instead of getting to play baseball with your dead heroes you have to awkwardly back away from the stunning guy who just crushed your heart. Life is illusion, society is held together by intangible bonds, and hotties will shun non-hotties without sufficient reason to do otherwise.
Of course, plenty of attractive people also have personalities, and thoughts, and feelings that cross such arbitrary boundaries. But if you're asking if there's such a thing as an unattainable guy, there most certainly is (unless your friend was referring to some kind of kidnapping plot). The good news is he's probably an asshole anyway.
To an extent, yes, every guys is attainable. If you want to throw yourself at a guy to be physical with him, there really aren't many who would turn you away. If you are looking for a relationship, however, there is no doubt that leagues exist. You may wow somebody and jump up a league with someone, but that can be a hard thing to come by. Confidence and intimidation are key. Confidence is for yourself, while intimidation is to make the other women, your competition, uncomfortable; intimidating the guy is a bad idea.
Hmm. . . is every specific guy (or woman) attainable? No.
But borrowing from the sports metaphor, any one person in one league can almost always "attain" someone from any other league. It just takes time, practice, and an ability to generate your own self confidence.
If you look at things statistically speaking there's evidence of "leagues". People of similar levels of attractiveness tend to pair off. People with similar levels of education tend to pair off. I myself beleive in leagues, but not in a strictly physical way. I think of it in terms of having class, you know like behavioral guidlines. People who steal all the time and punch others I would consider to be beneath my league of people. I just wouldnt consider dating someone like that. So basically, I base my "league" guidlines on behavior and not really attractiveness. Of course, I'm not going to want to date someone I'm not sexually attracted to, but for me sexual attraction is much more about swagger and confidence than physcial features. I hope that makes sense!