I have a colleague who has Asperger's Syndrome. He's told me a bit about what it's like for him but had he not told me about this I'd have just thought he was a little awkward and geeky (geeky being a very positive thing to me). To me that type of thing doesn't need a label, doesn't need classification as a disease, and probably doesn't need "treatment".
A label can go a long ways. You, after all, have labeled this person "geeky" which to you is a positive, but, alas, not so much to others--unless the geek is good looking, even sexy, as all geeks are on television. Geeky, after all, used to be a label that got you mocked, beaten up after school, and not taken seriously—and it is a label that assumes you don't have to be this way. The Geek who gets a make-over and becomes a "normal" person is a common trope. Even to this day, geeks are still mocked, ignored, dismissed, etc. And it is still assumed that they could be other than geeky if they wanted to be.
So, I'm glad that "geeky" is a positive to you, but it's not an accurate label, and it can be a detrimental label.
Aspergers is much more useful. A neurotypical person who meets a high functioning Aspie, and doesn't recognize the symptoms, will make certain assumptions. Like "he's ignoring me. Does he not like me?" or "he won't meet my eyes or shake my hands, does he have a problem with me?" They make assumptions based on what they know: if a neurotypical person acted this way it would mean "X". So your friend must mean "X" because he's acting this way.
If, however, your friend says, "I'm Aspergers," then the person he's meeting won't make wrong assumptions as to why he's not shaking their hand or meeting their eyes or looking off as if he has better things to do. They will understand rather than mistake. And they won't, as with the "geek" label, presume that he can be other than this if he'd just change his clothes and take a few lessons in social niceties.
As for "treatment"—the younger an autistic child can be diagnosed the better. The world is the world, and we all have to learn how to live in it. Neurotypical people make this world and embed in it things that they take for granted, things that an Aspie might not see (or might see very differently). It's a little like being colorblind. The world assumes you can see the color red and uses it for important things. But if you can't see it, or you see it in a very different way...well, you need to know this, otherwise you could be in trouble. If a parent knows their child is Aspergers, they can teach him how to see things he might otherwise miss or misunderstand, and, thus, have a better life. That is the end goal for any diagnosis isn't it? So, no, it's not a disease. But it is something that needs to be seen and understood. And it won't be if it isn't labeled right.