Sure, it might happen, in only the most extreme cases, but it's certainly not the norm, and it makes people who try to take their faith seriously - even if, yes, LaVeyan Satanism is simply libertarian humanism combined with, quite honestly, a fairly weak system of Ceremonial Magick, if it makes them happy, let them do it.

I don't agree with Catholicism, either, but I'm not running around saying all priests rape little boys, even though there is far more evidence of that, than actual human sacrifice in Satanism.

The latter do tend towards being the awfully nice people you've been describing, who are always making sure that everyone is fine in the mosh pit.

The former, however, can conversely tend towards the type of person who is far too enthusiastic about the technical details of the blood gutters in their unnervingly large collection of ceremonial knives.

There are plenty of theistic Satanists I know who are also great people.