Atheists say there is no god
As rhetorical shorthand, yes. Technically, atheists don’t like to say “There is no god” because then we are making a positive claim about reality. Some theists like to quote the bible, “The fool has said in his heart, ‘There is no god.’” I like to follow it up with “And the wise man says it to the world.” I didn’t come up with that, but I think it’s clever in a bumper sticker sort of way. The point is, we believe none of what theists say about god or religion. We definitely think each and every religion is absolutely wrong about reality and about human nature and life and the earth and the universe and how it all came to be, and that if there is a deity, it is absolutely nothing like what any religion has ever claimed it was.
Atheists want to take god/religion out of public life
This one is actually true to an extent. Atheists and secularists reject the encroachment upon civic life by religion, outside the church and the home. Say all you want about god(s) in your home or place of worship, but schools, government buildings, the military and such, those are off-limits for theistic beliefs (if propounded by figures of authority). Atheists are secularists and feel civic life must be neutral on religion, neither for nor against--as of course do many theists. One can be both a religious believer and a secularist. That's called being an American.
Atheists have assumptions
No, atheists have conclusions. Some theists accuse atheists of assuming something called “naturalistic materialism” is true, and basing our beliefs on that. “Naturalistic materialism” or “methodological naturalism” is how science goes about figuring out stuff works. It has no need of the “supernatural” to conduct its experiments; indeed assuming there is a supernatural world would gum up the workings of the scientific method that gives us stuff which everybody, including creationists, likes, such as vaccines and airplanes and heart transplants and insulin shots. It is an attempt to understand the natural world. The atheist sees that there is simply no evidence in that natural world that reveals any type of deity, and has come to the conclusion one, or many, or an infinite amount, do not exist.
Atheists have killed more people than the religious
Certainly totalitarian regimes have killed millions in the 20th century, more than the Inquisition, say. But if Dostoevsky’s Grand Inquisitor had had access to machine guns, gas ovens and the like, you can bet he’d have been using them. Leaders drunk on power and believing themselves invincible can be found throughout history, secular and religious alike. But even besides that, even if atheists killed more people than anyone ever, that would not be one bit of evidence for or against the existence of a god. Atheism isn't necessarily about what's good for society; it's simply a lack of belief in theism.