Criticizing a Las Vegas ad for being too base is like criticizing the wind for blowing - that's just the way things go. But even with the standards set about as low as possible, this just seems wrong somehow.
So... let me see if I get you, Vegas. You are aligning yourself with... Satan? That's really the way you want to play this? I know, the nickname is already Sin City, but this is significantly more explicit. The viewer is being encouraged to go to Las Vegas and behave there like Satan would. That's way beyond "Come to Las Vegas and have casual sex while lying about your real identity" like most of these ads, isn't it?
Of course what I think is more likely to upset people - and I can't say I'd blame them - is the angelic sanction of devilish behavior (and then some). I tend to snort derisively when right-wing Christians claim that things like "Happy Holidays" are a tacit attack on their faith, but an ad like this? I wouldn't fault anyone for calling it blasphemous, and in fact another version of it on YouTube does just that.
I'm not personally offended by this kind of thing, but really I just don't get it. What is the Las Vegas Tourism Board, or whoever specifically puts these ads out, hoping to achieve by assembling something so far over the edge? It's hard to imagine you're going to win more people over with such an ad than the large number you could potentially turn off - the United States is still overwhelmingly Christian and there are plenty of things to do in Vegas even if you're not into contracting gonorrhea. No one is watching this and thinking, "Oh man, dude, Vegas really stuck it to the Jesus freaks. Let's go there right now."
The very end of the ad is the worst part, and it doesn't even have anything to do with the Devil - frankly, it does offend me a little bit, and that's hard to do to someone who isn't a member of the religion you're mocking. The use of "I can get you in upstairs, I know a guy" is a double meaning - both a suggestion that the angel can get the women into an exclusive club (for which they might, perhaps, reward him?) and, of course, a reference to getting them into heaven. Put it together and the angel is offering eternal salvation for a blow job. We may need to get Martin Luther to nail 95 more theses to the door of the MGM Grand.