OKC, I totally see what you're saying about it being hypocritical but most of what happens in GTA is either a sort of homage/pastiche (Scarface being a big example) or making fun of something like "TrueGrime" where they joke about how lame it is. What's happening in the Simpsons here is GTA is (once again) being made to look like a slaughter fest, which is much more detrimental to it's image than any mockery (not to mention totally inaccurate).
What Ash posted here sums it up:
Originally Posted by ash_735
To be fair, there is doing a parody, and then just overkilling it, The Simpsons has spoofed GTA many times, Grand Theft Walrus, Grand Theft Scratchy, Death Kill City II: Death Kill Stories, and each time, it's always shown the games as some sort of slaughter game. Now people who know and play the game will know it's a joke, but The Simpsons is a family show, if they keep seeing references to GTA and them being totally overly violent, with people slashing each other to pieces, then yes, it's going to cause bad publicity and will encourage those sad soccer moms to complain about the real one even though they don't have a clue what it's really about.