Men's Bodies: Gross!
No, but not in the way the article is trying to make it a general issue. OK, those half-thongs are stupid and ugly, mostly because the asymmetry is offputting and regular thongs get similar jeers. The problem isn't male nudity: the problem is men and nudity.
I think the problem the Guardian writer - who is, incidentally, a woman - is noting is more an issue with male discomfort in seeing another man naked. Men feel a primordial threat in seeing a naked attractive man nearby; he's going to usurp your manly place in the order of things, or possibly use that manliness against you to assert dominance. Since there's a pecking order, you put down the other guy to assert your own dominance, you point out the unattractiveness, the ugliness, to bolster yourself. Men, particularly those trying to put on an extra-super-straight exterior, are uncomfortable with seeing a man naked because of the threat against his own sexual power. And that's stupid, really, porn is full of naked guys that embody the wishes of the watcher; the urge is to be the guy who's fucking women, not to be the guy standing on the side while the sexy, attractive naked guy does the fucking. Seeing the naked male form stirs worries of the latter, which is something guys need to get over, the pissing contest hasn't worked since caveman days.
But, on the other hand, just look at this guy: