I've noticed that many of the Chinese counterfeiters have migrated from eBay (where replica sales have been banned) to Amazon, where they can flaunt their "goods" with little or no interference.
I consider myself a bit more than a novice with early dates and variety attribution. But I am easily fooled by these since I'm not familiar with the Late dates. But even those I'm familiar with will fool me if they get the variety details right. And I do not trust TPGs with variety attribution. They have too little time to spend with the coin to get it right unless it is a very easy attribution.
Actually it is neither unethical nor illegal to sell them, as long as you make it clear when you sell them, that they are counterfeits/fakes. If, however, you sell them as genuine coins, knowing full well that they are fakes, then yes it is unethical and illegal.
EBay eliminated the "Replica" category; however, you are correct... the fakes are now intermingled with the genuine coins. This meager attempt by eBay to end one problem merely created another problem. Still, many of the volume sellers (of unmarked replicas) have set up shop on Amazon and other similar sites.