It's a perfectly valid argument if it's over game mechanics or rules. Those are not copyrightable, and while it is ethically questionable, there's nothing ille

It's a perfectly valid argument if it's over game mechanics or rules. Those are not copyrightable, and while it is ethically questionable, there's nothing illegal about copying mechanics completely while putting a new skin onto the game. It's less valid if it's copying art or sound assets. Unfortunately, this discussion isn't about mechanics(as tbaltree notes in the thread), it's about the specific art assets.