Some Atheists can be just as self righteous and judgmental as Christians/religious people. Change my mind......
The "some" in your question implies that such attitudes, while existing among Atheists, exist to a greater degree among Theists. I would agree to this. And for 2 decades I could not bring myself from the position of Agnosticism to that of Atheism. That required the knowledge I've since acquired from digging deep into information that was not readily available to me at the time. That many Theists have never even questioned their beliefs and/or are often discouraged from doing so, it is no wonder that the named attitudes would be more prevalent in them.
I can be self-righteous and judgemental and I’m neither!
Who cares, the facts are on their side. We are just as self righteous and judgemental as Flat-earthers too.