I think anti-languages are something that evolve naturally, not necessarily because of a specific requirement -- like talking about criminal activity. It's just lingo really, look at any online community and they all have their own language which is born of convenience and familiarity. My wife and I have our own of sorts, where words have been bastardised, such as computer -> computner -> putner, or where specificity is given through context, dooper -> remote / phone / thermometer / keys.
This is more applicable than ever online. If we examine (and I'm sorry for this) chan-speak, it is designed not only to confuse outsiders but to repulse them as well. The repeated use of homophobic and racist slurs seems partly there to put off the people called "normies" in their language, as well as simply being an in-joke. This might be an added layer of secrecy, thus causing people not in the know to dismiss them all as foul-mouthed bigots (which it is of course entirely possible that they are).