So, it is your considered opinion that if you were in a burning theater and and the theater manager came in and pointed to the bathroom door and yelled 'That is the exit'. It would be perfectly okay, and he was just 'exercising his first amendment rights'?
It was not pointed at me, but let me answer it for you anyway. Yes, people should take the advice of leaders. That is why we have leaders. To lead. They are supposed to be informed. They are supposed to consider what they say and give us good advice. The moment you start saying 'Why should we listen to Trump about X since he is not an expert' I have to question why we should listen to him about anything? He is not an expert at anything we elected him to do. So, why is he even having press conferences? He is not expert at any of this.
People elect leaders to lead them, because we simply do not have the ability to learn everything for ourselves. The President is supposed to be the megaphone broadcasting the real experts opinions, not making up his own. That is why people take his advice, because they expect that advice to be coming from the best experts the most powerful person in the world could find to advise him.