I also think everyone is entitled to bring information and opinions. He did however say "if you are smart you will" in response to a post of "who would sell at these levels?"
Implying that it is stupid to be holding shares of a particular stock on a messageboard specifically focused on that stock isn't necessarily the most tactful way to go about adding ones opinions and information. Is it?
So I attribute the backlash to be a result of this lack of tact and maybe it is not necessary, but those with different opinions are welcome to share them in response as well I hope.
If I knew I was posting something that might be unpopular to the masses on a particular message board I would try my best to state the reasoning for my opinion and use facts and my interpretation of those facts to make my point. Even doing so in a respectable manner I might expect some lambasting, but at least I would know that it was only for my opinion and not the fact that I made my point in a potentially instigative manner.