Yes, he wasn't demanding it. However... like many other topics, it has been beaten to death repeatedly. Outside of that, someone else replied and started up with his reasonings to have it, so others responded with the opposition.
Lastly, the line "If you don't have anything nice to say..." would restrict people. Mainly because what one person considers nice or not, is not the same for everyone. So one person could simply say it's not nice, you shouldn't have said that. Even if the person had no hostile intent whatsoever.