can athesits or agnostics be into satanism?

Satanists ARE atheists. I should know as I am an atheist and an agent in the Church of Satan.

You were lied to. While the definition of atheism and agnosticism technically allows for belief in Satan and the occult, the vast majority of people who identify this way are rationalists and would find such ideas silly.

Perhaps you were confused with LaVeyan Satanism, a religion that doesn't worship Satan or have any deities, but calls itself Satanism because it takes a page from Satan's philosophy as expressed in the Bible (which to LaVeyan Satanists is strictly seen as mythological). Some atheists and agnostics may be LaVeyan Satanists, though not very many.

Satanists are elite atheists. I read the satanic Bible and I know real Satanists. Satanism is a philosophy though and not occult at all as they deny all things spiritual

No. If you are in to satanism then you're a theist.

An atheist does not believe in any deity. I see all religions and deities as equal; whether it's yahweh, allah, veshnu, or even Osiris, Zeus or Jupiter. I don't believe in any "higher power".

However a common attack used by theists is that, if you don't believe in a deity how did we come about, or what created the big bang etc. Just because something is unknown at this point; you do not need to conclude that it was created by a mythological creature

The largest Satanist organisation preaches a form of agnosticism that could easily lead to atheism so the answer is yes. But then there are a great deal of people who profess to be Christians who are actually agnostic and a large number who are actually atheist.

An agnostic may be, but most atheists laugh at satanism like they do other religions. Though some atheists may play with satanism to show others how goofy any of them are.

Atheists do not believe in God or Satan, so do not practice either religion. Agnostics think there is God but He is not active, no satanism there. If these people were doing those things you mention they would be labeled satanists etc. Anyone can do many of those things at once if desired.

If they do not believe in a good God, or God at all, what's stopping them from going to the

other extreme? (evil), really where are the boundaries?

No. Completely opposed schools of thought.

I think your confusing babby eating with satanism