He can't buy unless they want to sell. That hardly constitutes a "threat" to them.
The constitution IS the basis for our democracy, and upholding the constitution is a rather critical part of protecting our democracy. Perhaps you don't fully understand the 1st ammendment - many non-US citizens don't, even if they say the believe in "free speech". But much of what you have proposed really would violate the 1st ammendment, and you seem not to have noticed this or really cared about what that really means.
Much of what you describe requires subjective analysis, for one thing, and for another, the day the government gets to decide what's the "truth" and punish those who say anything differently is the day that free speech dies. We already have mechanisms to protect against libel and slander (which are civil matters, BTW), but beyond that, I don't want the government having the ability to punish anyone for saying something it deems to be other than the "truth". Because you cannot give the government the power to punish people for telling lies without giving the government the power to decide what constitutes the truth, and that is quite frankly a VERY scary prospect. How did you miss this implication to your own proposal?