The beliefs in supernatural phenomenon, an afterlife and the infallibility of religious doctrine are dangerous. There are many reasons that they are dangerous. For one, books like the Bible are open to millions of interpretations because there's no objective standard to assess its content. Also, you end up having to believe that highly immoral actions are moral simply because the god of your religion has been defined as the source of objective morality by the scriptures themselves. Therefore, actions like genocide, infanticide, abusive slavery, sexism, racism, animal cruelty, stoning and many more wonderful ideologies and practices are moral when this imaginary being says so in his fictitious book.
Atheism has no dogma or creed. It doesn't make unsubstantiated claims. There's nothing taken on faith. It doesn't even mean that you automatically believe in evolution.
Arguably, the most destructive force against humanity has been the belief in religious doctrine. The 911 attacks, crusades, Spanish Inquisition, and Holocaust can be directly linked to religious doctrine. When has not believing in something merely on faith caused mass genocide or terrorist attacks? People become slaves to beliefs that have no evidence and find the motivation to kill others because of their interpretations of scripture. God's will supersedes humanities, and it makes killing more palatable.
In the case of the holocaust, we can thank Christianity for antisemitism and the killing of millions. The Jews are responsible for killing Jesus of the Bible, and Hitler took this ideology, inspired by Martin Luther, and enforced it systematically. The scriptures offered no foresight into the events of the Holocaust or stern warning against killing the "children of the devil." Perhaps Jesus was only addressing a certain group of Jews. Nevertheless, scriptures like these fueled hatred for Jews, and god, with all his wonderful foresight, did nothing to prevent the deaths and persecution of Jews.