An atheist is someone who does not believe in any gods, there's no associated personality or behavioral traits attached to that.
An atheist could aggressively push his/her viewpoint on others, but so could a religious person, it's a personality trait independant to their faith or lack of faith.
There are no rules of behavior that apply to all atheists because it is not an organized religion. Some atheists are very respectful of others and some are not.
Atheism isn't a belief system, so there's no reason why atheists would share the same beliefs. So, doubtless, some atheists believe in evil and some don't.
Negativebehavior is behaviors that are bad or naughty.
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Some atheists do. However, the hypothesis that religious belief is facilitated by genetics is not universally agreed upon by atheists. This is not a central concept of atheism.
Use of negative enforcement to encourage desired behaviors
Use of negative enforcement to encourage desired behaviors
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Some atheists do. But it is impossible to cover such a large group with a generalization like that.
There is no "official" atheist symbol as there is no governing body of atheists. The US Military has developed a symbol (stylized atom) to mark military graves of atheists and some atheists use a red "A" on their web sites and blogs.
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Enabling - this implies that the support given may actually hinder or perpetuate negative behaviors or situations.