Sorry, but I still do not see what is bothering you so much.
So what if Colin Powell gave an opinion based on incorrect data?
People do that sort of thing all the time, however that does not mean that they are bad people. Instead, it means that they gave an opinion based on incorrect data.
That is a great question and I will try my best to answer it!
Now then, if Powell was giving his opinion on something and that opinion was based on incorrect data, then that is still considered Constitutionally protected speech.
I hope that is clear, because now I would like to show you something a bit different.
Suppose, for the moment that Powell held a very high office: like the US Secretary of State, for example.
And suppose that Powell was addressing an international body as the personal representative of the United States: like he did with the UN on February 6, 2003, for example.
And suppose he was there on a very important and very official job: like proving how urgent it is for the USA to go to war with Iraq, for example.
And suppose he said something like:
"there can be no doubt that Saddam Hussein has biological weapons and the capability to rapidly produce more, many more."
And then he went on to show diagrams of mobile production facilities for biological agents, as well assure everyone that he was speaking of facts.
Well, this sort of thing is not an opinion, and such it is not Constitutionally protected speech.
I hope that this point is clear as well.