Learning about either topic takes precisely as long as learning about the other --a few months, years, or a whole life-time. The point when you decide you've learned it all and stop learning is entirely up to you.Certain Sciences can be taught at just about any school or college in a matter of months, learning about religion can take years. The understanding of religion cant be accumulated for in that such of a short time span. If atheists have that type of mind set or mentality where they just want everything handed to them and explained because they have a barrier around their own belief system, what good is it for someone that actually takes time to study and practice a religion to tell someone else about it that really never had any interests in it to begin with?
While I agree that many atheists have no interest in learning about "God", it's not what defines atheism for me. Even many theists have that type of mindset where they just want everything handed to them already explained --by the church, the synagogue, the temple, etc. These things don't characterize atheism in particular, just people.