If we give that power to the government, the people will be slowly choked into not speaking their mind about anything. The biggest issue I've seen for a government "needing" to step in is the issue of bullying as a form of freedom of speech. It should not be the government's responsibility to restrict us. It is the people's job to assess these problems and find the solution. People can take responsibility if we give them a chance. The government won't give them a chance.
No. The government was set up based on a simple set of rights for all people, and freedom of speech was at the top of this list. Freedom of speech is important for people to pursue happiness and liberty. If the government took it away, the people would eventually have nothing to pursue since they would know the government would eventually take that as well.
The government has no right to prevent me from saying things unless it hurts someone else. For example I can say that I don't like President so and so but I shouldn't be able to threaten to kill a man. I can state that I like this football team or believe in this religion anytime I feel like it and the government should not stop me from doing so.
A government should never be allowed to limit what someone says. The only reason a government would want to control speech is if they are trying to cover something up or trying to get the public to turn a blind eye toward an act that it committed. If the government controlled all speech then the people would be constrained by what the government tells them and that would not be acceptable.