See, I think Joffrey has already successfully been established as cruel, heartless, etc. Not a minute prior to that scene, they show him pointing an arrow at Sansa, threatening to kill her, but he then decides to have his guard rip her dress off and beat her with a sword in front of a crowd of people. This is after the fact that he had her dad's head cut off, has had his guard hit her before, and is just generally a massive douche. The subsequent prostitute scene was complete overkill and just not necessary and a waste of time. I mean, I get that they have some kind of boob quota for HBO programming, but they could have used those boobs to tell some other part of the story.
They could have used that time to actually make Catelyn not sound like an idiot when Stannis and Renly met (her words during that scene in the book were so much stronger), or to flesh out some other part of the story. I get that they were trying to make a funny, but it just lost the weight of what was happening. Instead, so much time has been devoted to the "Renly's gay" which really, truly is not relevant to the story at all despite the fact that it's hinted at in the book. It just isn't, especially considering what happens to Renly. And because they've decided to place importance on this, we've got Margaery and Littlefinger running around yaking up a storm when they shouldn't be.