Mayweather is not known for having KO power in his punches like Cotto. Everybody knows that anyone else would probably go down in the first rounds with Cotto's power punches. To see Cotto punching away only to have Tony walk through his punches with ease made Cotto look silly. Imagine Tyson, in his prime, punching a guy directly to his head many many times only to have him walk through them as if he was being hit with pillows. That would be humiliating. Oh man, it would have been priceless to see Margarito pull off a Mayorga stunt and taunt Cotto making fun of his punches and later have the referee and his corner save Cotto's life.
So when Mayweather and Tony finally get it on, and Mayhweather runs off all night punching Margo in his head, and wins a wide UD Who will look silly then, Mayweather for punching a man who could take them all, or Margo for losing a Wide UD
That is Mayweather's style and he has won like that numerous times so its nothing new really. Mayweather is known for getting on his bycicle to win. Now, Cotto and Margarito are known for the power they pack in their punches and how they can KO a guy with a punch so having someone walk through their punches can make them look silly. Wouldn't you be intimidated to know how you KO guys all the time and suddenly face a guy who walks through your punches? Cotto's fear/intimidation was clear.