You are free to criticize atheist people and atheism .you can campaign against their logic by giving logic.Atheist are also free to criticize any religion like you.This is the only way to forward human civilization,To do criticism and receive criticism,upholding freedom of conscience and thought.No religious,political or any other holy figure should be above criticism,if any holy figure can't tolerate criticism then there is nothing holy about him.
Why do you want to uphold islam by suppressing criticism of it?If islam is perfect than it can overcome criticism.If you want to live in a democratic society and state then be prepare to receive criticism of your belief,your political orientation.We all have to remember that life is sacred,not the belief system.State have the responsibility to protect life irrespective of religion,political orientation,ethnicity,not the belief of any particular group of people even if they constiture majority.
Belief,religion are something that we are not all agreed upon.One man's belief is another man's blasphemy.So protecting the dominant group's belief system will only make the state tool of oppression and injustice.We all have to criticize one another's belief so that we may reach nearer the truth as you may not know the whole picture if you only exposed to one side of the argument.