I don't know about Mayweather ruining the sport of boxing. That's perhaps a bit harsh, but it destroys Mayweathers credibility that he is seemingly so unwilling to face a true welterweight these days. Even Mayweathers fans admitted that a Marquez gimme would only be a one off and then time to face a proper fighter. Manny is not really a proper WW in my eyes anyway (145 catchweight=poof) so Mayweather really needs to face a credible 147 pound fighter or else he will look like a class A clown too. Mosley is out there, there is no reason not to make the fight. And Mosley is 38, surely Mayweather can't pass up that kind of opportunity.