I often hear talk about atheism as if it is an ideology. People often think that atheism is the same thing as communism and must be bad because of that. I don't think this is the case. I don't think either atheism or theism are ideologies.
Theism is simply the belief in god or gods. And atheism is simply the lack or rejection of that belief. Theists believe for many reasons, and atheists disbelieve for many reasons. But there is nothing else that is, in my opinion, inherent in either of these positions. What I mean is that someone being an atheist or a theist only tells you one thing about that person. And that's their belief with respect to god or gods. I don't want people to pack anything else into this position because I think it's dishonest and disrupts the integrity of already easily usable words.
Because atheism and theism can only tell you about one aspect belief system, I don't think either can be ideologies. Ideologies are packed full of extra views and values about a great many things. Ideologies can contain atheism and theism. There is no question about that. But they cannot be ideologies in and of themselves. It seems silly to me to even make that claim.
Now I do think that religions are ideologies or, at the very least, a type of ideology. Religions have a lot of values and beliefs about the world in there, and I think this is basically the same thing that ideologies have. And because of this, I don't think that atheism can even be called a religion. Atheism can be part of a religion sure. There are religions like Jainism that are totally atheistic. Jains might carry around a bunch of other metaphysical baggage around, but they don't carry any baggage called God. And as we know, most religions are theistic.
There have been terrible ideologies and/or religion (however you care to think of it) that include either atheism or theism along with them. Stalinism is a great example of a terrible ideology that included atheism as part of its inherent belief system. And Inquisitional Catholicism is an example of a terrible ideology (or religion if you prefer) that carries around theism. But the terribleness of both of these ideologies says nothing about atheism or theism. Only the ideologies themselves are responsible for the crimes that are a consequence of that particular ideology and can be judged by those crimes.
The problem with with religions and ideologies is faith and certainty. It's the lack of questioning and the ability to accept something on authority along regardless of what any evidence to the contrary may say. Monolithic and unquestioned beliefs are the problem.