Ok, let me explain to you people what Satanism really is, since it is quite apparent none of you seem to understand...
Satanists do NOT actually worship the mythological Christian devil, called "Satan". The name "Satan" is translated to mean "Adversary". So when Satanists call themselves Satanists, they are implying that they are adversaries to the Christian religion. And modern day Satanism, aka LeVayan Satanism, one of their foremost rules is to NEVER HARM ANY CHILD. There is also some text in the Satanic bible that even puts animals in a higher position above humans... the LeVayan concept of Satanism is actually more an atheistic philosophy than anything. Many Satanists today are actually atheists. They used the symbol of Baphomet as more of a symbollic figure, but many people assume it means they are worshipping the devil. It is all symbology people. They do it to get the goats of a lot of Christians... and it works.
Also, mant Satanists follow a version, their own form of the Wiccan Rede "An harm ye none, do what thou will." Also their are Luciferians out there who worship the Roman God Lucifer, either as a deity or symbol. Lucifer was originally a very noble Roman God... he was the son of Venus. The name Lucifer however became drug through the mud with the rise of Christianity and Islam. Luciferianism, many people attribute as a form of Satanism in itself, but in actuality, it is a very old Pagan religion that pre-dates Christianity by thousands of years.
Are there people out there who ACTUALLY worship the devil as a deity? Absolutely! But how they see it, is that Satan is the father of all knowledge... since he tempted Eve to bite of the forbidden fruit, giving humanity all of the knowledge we have today. They see Yahweh as the evil, trying to repress knowledge for all of manking, and as a bully for kicking Lucifer out of heaven for blessing mankind with all of this knowledge. In this case, Yahweh is seen as a dictator of sorts, and Lucifer, AKA Satan is considered the true hero.
A very small minority of Satanists ACTUALLY practice animal and child sacrifices. This is just superstition and rumors spread by the Christian church. The figure Lucifer doesn't even rightly belong to Christianity... Lucifer is a roman God of light. And like I said already, the name Satan, translated, literally means "adversary".
My own personal opinion of Satanism? I don't entirely agree with it's concepts... such as seeking revenge, never sacrificing for others, and for the sheer fact that I don't agree with the concept of Autotheism, which is quite literally, the worship of yourself as a God. Satanism is actually an Autotheistic religion. Satan/Lucifer/Baphomet is used only as a symbollic figure in most cases. A select few actually worship either Satan or Lucifer. An even extreme smaller minority actually practice animal and human sacrifice... if any of them at all.
I personally don't believe in a mythical "devil" that goes around and causes us to do all of these nasty terrible things. I believe if I screw up or do something bad I must take account for my actions, instead of blame a mythical devil figure. I do however believe in bad spirits that like to cause trouble... but a devil? Nah. That is just rediculous. The Satan figure was made up by the Roman Catholic church to scare people into converting from their older Pagan religion to Christianity/Catholicism. After awhile the Catholic Church itself started assimilating Pagan beliefs with their church.
To sum it all up, people, Satanism is the concept that everyone is the master of their own destiny, and that supposed "sins" are completely acceptable as they cause emotional, physical, sexual, and/or spiritual gratification.