If Tiger Woods had been the one who lost, and then said that, there'd be furious tweets and angry columns for weeks, denouncing Woods for having the nerve to say something like that. Doesn't he care? How dare he make light of losing!
Not a criticism of McIlroy, by the way. Just an example of how fans' natural biases cause us to react differently to different people and different situations. Marion Jones is a pariah because she doped to win her gold medals; Lance Armstrong doped to win his Tour de Frances, but, hey, he beat cancer! If only Marion had had the foresight to get a terrible disease, and then attach her name to a charity.
We all bring biases. We all have filters. If you love Tiger, you filter everything that happens to him and everything he says and does through a positive light. If you hate him, you do the opposite. Two players, one you like, one you don't, can say or do the exact same thing and cause two different reactions in you.
That's human nature. But it's also something we should always keep in mind when we're praising one athlete or raking another one over the coals. Always keep your biases and filters in mind. It's not wrong to have such filters, it's only wrong to deny them.