A rational society would classify it as a fetish, like feet or leather. So long as the affected person did not suffer or harm others, it would not be classified as a disorder. Instead of this rational approach, however, we've chosen to swing from one extreme to the other -- now homosexuality is an "identity," like Jim McGreevy the "gay American." Had we been more rational, that would've been as remarkable as Joe Schmoe the "foot-sniffing American," Hans Kent, the "American Who Likes to Wear Women's Underwear But Only in the Bedroom," or James Hammel, "the American Who Prefers Blondes."
A former co-worker of mine once regaled the office with a story from her 9-year-old niece's birthday party, at which one of the boy guests repeatedly smelled the girls' feet. The niece would yell "MommEEEE! He's sniffing my feet again!"
The co-worker was horrified by this behavior and went on at length about how it was creepy and pathological, and the kid needed to be locked away from girls until he could be cured of his obvious sexual wierdness.
Which was all well and good, except that the co-worker was a lesbian.