The issue that people have is that there were a few things working heavily in Hendricks's favor. The first is that the crowd was behind him, because he is the first guy to give GSP a competitive fight in six years. That means that the crowd was reacting more to his shots than they were to GSP's which made them feel more powerful.
The second thing that was working for Johny was Joe Rogan. I'm not saying that Rogan is biased towards Hendricks; I really think he just got caught up in the moment, but either way, his commentary was definitely biased towards Hendricks. When GSP hit a strike, he would note that it was a nice shot by Georges. When Hendricks landed a shot, he would say, "That was a HARD shot from Hendricks." It made Hendricks's shots seem like they were a lot more powerful than GSP's. Now I think that judging the power behind shots from television is incredibly difficult, so it may have been than Johny was landing harder shots, but I do not believe that the difference was as pronounced as Rogan made it sound.
Finally, the third thing working for Johny is that he doesn't bruise easy and GSP does. GSP has always bruised easy (Fedor Emelianenko had this same issue), so even if he was landing better shots, he was the one who looked worse at the end of fights. This gave the impression that Hendricks did far better in his strikes but basic skin damage is not a way to judge who won a fight.
Because of all of these factors, people thought that there was going to be a new welterweight champion in the UFC. There wasn't, and I have no issue with this. According to FightMetric, Hendricks outlanded GSP in strikes by 17 through the fight, but GSP outlanded Hendricks in significant strikes by 16. Just because the majority of people leaned towards Hendricks in a close fight does not make this a robbery.
It was a close fight and GSP got the win. The judges don't need to be fired for that. There are a lot of really awful decisions in MMA, but this isn't one of them.
With all that being said, I would have given the edge to Hendricks.