Didn't really read all the responses, but I'll throw in my $.02 in simple terms.
Tennis is special because when it's played without an official, the opponents must exhibit a significant level of integrity and mutual respect. We call our opponent's shots out there, not our own. That's a rare thing in sports, but it's also especially worthwhile. As a "tennis person", I take some extra pride in my sport because of the sportsmanship that's woven into the fabric of the game. According to its code, points are only earned and opponents receive the benefit of the doubt without hesitation.
Anyone willing to take up these responsibilities as a participant at least earns that extra measure of respect from his or her peers. Those who cheat in an attempt to get by out there are frankly disgusting. They have no respect for the effort and skill of their opponents OR the benefit of the doubt which those opponents are willing to extend them. They also don't respect a sport which spans the globe. I have no tolerance for such arrogant turds.
Anyone who believes they're "obliged to cheat" are cop-outs who are lying to themselves to justify their conduct. They have no interest in a true sporting contest where they're willing to put their skills and tactics up against those of a worthy opponent. They're bad for tennis. They deserve no respect or courtesy from other players if they think that they can chronically cheat. They'd be better off in some other athletic endeavor where their responsibilities are managed by a third party who carries a whistle.
On a lighter note, the cool people rarely invite the cheaters or weasels to their parties, so there's that...