The making of a distinction between "real" X and "phony" X (where X is a member of some religion) is a Christian tactic, not a Satanic one. After having so often been subjected to Christians "dropping their tails" whenever some unsavory aspect of Christianity is brought up, and saying, "Oh, those weren't *real* Christians", I am hardly going to play the same dishonest game myself. There are only two cases where I would go along with saying that someone is not a "real" Satanist. The first is in the case of measurable insanity. Psychotics frequently have elaborate delusions involving God, Satan, and other aspects of mythology; a belief system like this does not deserve to be called Satanism, Christianity, or whatever. The second type of "unreal" Satanism is outright fraud. For instance, Sean Sellers blew the head off a convenience store clerk with a shotgun. At the time, he claimed it was because the guy had flirted with his girlfriend. Later, after consulting with his attorney, he decided it had been a sacrifice to Satan, but that he had since become a born-again Christian and wasn't some leniency called for? This is fraud Satanism (as it is also fraud Christianity).
As for whether teenagers and dweebs playing Satanist are dangerous, I think the danger is overrated. Some people who would be dangerous anyway may decide that they are Satanists, but there is no evidence that Satanism has ever been the *cause* of any violence or anything similar. People who feel alienated from society and who feel that society has deprived them of their just amount of power certainly can be dangerous, and obviously some such people will be attracted to the Prince of Rebels. If anything, this psychodramatic outlet nd opening into the philosophical realms of myth is more likely to do them good than the other outlets, such as youth gangs.