That's all fine and good but then that would be a two way street. Yes, no one gets to use that argument on a game you like but in turn no one gets to use that argument on a game you don't like.Agreed. This topic should be banned for life.
In reality, though, it won't be a banned topic. It's not just a matter of jabbing at games, people bring up sales figures as historical reference, to see how a game they are invested on is doing, to verify chances for a sequel, or just out of curiosity. Some of my favorite games never made it passed the 50 thou mark but that doesn't change how much I like them and I know this because I've looked them numbers up and I will argue their value despite their sales so it's not as though I've been on that side of the fence. It's too integral a part of game to be a forbidden topic.