I think we ought to be careful not to confuse human qualities of fanaticism and brutality with the qualities of certain religions. While it is true that some religions are better than others, these qualities are inherent parts of human nature, religion or no religion. We are just more used to seeing these qualities in a religious setting, because most human beings are, after all, religious. But it's worth to note the non-religious versions of those qualities as well. A few historical examples:
Violent extremism:
If us humans are not forming violent, extremist religious movements, we will form violent, extremist ideological or political movements. For example: the ISIS of the 1970's was the communist Khmer Rogue. In four years they killed 25% of Cambodian population because they thought the country needed a fresh cultural-economical start:
https://en.wikipedia.org/wiki/Cambodian_genocide
Persecution of heretics:
If us humans are not persecuting other humans based on religion, we will persecute them based on other qualities, such as race, political ideology or economic status. For example: The equivalent for the persecution of the Gnostics is when the atheist Soviet Union decided to eliminate the class of small farmers called kulaks.
https://en.wikipedia.org/wiki/Dekulakization
Twisting of religious ideals:
If us humans are not corrupting and twisting religious ideals into violent versions, then we will be twisting ideological or political ideologies into violent versions of the original ideas. For example, in defense of the noble ideals of humanism and democracy, the non-religious French revolutionaries in the 1700's engaged in an infamous campaign of terror and mass executions:
https://en.wikipedia.org/wiki/Reign_of_Terror
If we rid ourselves of religions, we will be dealing with the exact same fanaticism and brutality afterwards as well. Only in some new, non-religious forms.