I agree with you to an extent, but I personally wouldn't go as far as banning the user. Maybe something smaller like mute the user for 24hrs, then longer duration of penalty if he/she ever did the same offense.
I usually don't like calling out a website/person without an explanation or sources as well. But sometimes some websites and or ICOs just has too many red flags, being so obvious that it's a scam that I wouldn't need to give any explanation why. But yea, having an explanation why is still always better especially so the less-informed can know why.
I personally actually support this. As long as factual proof or personal doubts are explained. The same goes for shilling a coin btw. But i think fudding intentionally does more damage.