Which will always lead to immorality.
In theory though, they can always argue that following the GOlden Rule is good enough for them. If they strive to follow that rule, it i shard to argue that they are necessarily immoral; at the very least, it becomes ridiculous to argue they belong in the same category as child abusers and those who perform and celebrate abortions. Actually, equating atheism to sexually assaulting children is, to be sure, ridiculous in general which was my initial objection earlier. And would argue that same thing for, say, Hindus, Buddhists, Sikhs,animists, Taoists, pagans and Confucionists?