I fully understand the idea that some things, when taken too seriously and confused as being factual, can lead some people into an irrational world of evil, darkness and insanity.
However, I don't think RPGs (though I've admittedly never played one) are the main culprits here. I think religion is infinitely more dangerous when taken seriously, and far more people are led, through it, it's 'scriptures', leaders, communities and teachings into a world of darkness, hatred, evil and insanity where rational thought and common decency no longer mean anything.
However, I would suggest that for the sake of their own mental and pyhsical health, people maybe play them a little less. Of course, if you want to get rickets from lack of sunlight and go days on end without seeing another human being in the flesh, it's not for me to stop you.
peace