Of course it is "possible" for atheists to be called Epicureans. The question that has to be asked is "Is it proper to call them Epicureans?" And "In what context is it proper or improper to call them Epicureans."
Ok. And what is the proper context to say that an atheist can become Epicurean? I'm an atheist and I don't know if it's proper that I am here. I'm curious.