No we cannot, the difference is, gays do not have a habit of actually killing people for offending them or otherwise limiting the rights of homophobes. If they did, then this game would be a good thing and an act of defiance.
Those "acts of defiance" are the reason why we can't all get along, you know? They're never
a good thing. All those people too stupid to let go of the past, forgive each other and see that the other side is human, too. I suppose this has to do with both sides being made up of humans... Drawing Muhammad specifically to piss off Muslims is just as wrong as things they do to piss us off. It's equivalent to harming cows in India or mishandling the communion bread and wine in a Christian church. I couldn't care less for a bunch of cheap wine and poor bread, but they do, so I know better than to mess with those, even though I'm not fond of Catholic Church. I'd strip them of tax exemptions and special rights, but they can have their holy bread. Being a jerk about things that don't actually affect you is stupid (strong words about actual problems are OK, just make sure those are real problems).
Myself, I think that going out of way to offend each other is one of the few things worse than going out of the way to avoid offending anyone. If you have to, offend yourself.
The only group that has full rights to use a slur is the one the slur refers to. Indeed, you see that happen pretty often.
Regarding the game, I think it was really an insult to Steam more than anything. Hatred had some merit (though not a lot of it), this was just a pile of manure in every bit. The biggest cost involved in making this game was likely the 100$ for putting it on Greenlight. I'm not really against Steam selling it (the days when being on Steam was an indicator of quality are long gone), but it shouldn't advertise anything like that, simply because it's not worth any actual attention.