Why are people hating on Anderson Silva?

Okay i get it that he was getting dominated but still pulled off a submission which is a win.and i dont get why people are comparing this to machida vs Shogun and penn vs edgar. the whole point is that they both won by decision! which leaves the question who really won that why there is a rematch.and Anderson Silva finished the fight HELLO!Sonnen doesnt deserve a rematch he lost he tapout he got anderson ball sweat on his face. besides he said he would leave mma if he didnt win so leave Sonnen