Then, later, I found images like this image:
For something that ISN'T a belief system, looks like they sure are trying hard to proselytize. Now, granted, this group does not represent every atheist.
One problem in our modern culture is that the word "myth" is widely believed to mean "lie." A myth is a system of shared sentiments, a truth (the opposite of a lie) which can be communicated no other way. Calling someone's belief a myth is not, in many cases, supposed to be an attack on those beliefs.