Because the way it worked, when it worked, was we let people open their mouths, and called out what that pie hole said. Usually it was something fucktardedly stupid, but any ideas that came out could be worked with into something decent. Unless they were fucktardedly stupid.
For example, "Nazi's will save American Jews!" Imagine saying this in America in the 1940's.
You, on the other hand, decide to classify ideas you don't like as "offensive." Ideas that aren't fucktardedly stupid now become offensive, and facts now become fucktardedly stupid- for you. Those good ideas are eliminated beneath threats of lost jobs and social ostracizing because you screamed louder, and got well funded organizations or violent assholes to silence people through law loopholes or violence.
Instead of the previous statement, you have transformed it into "Let's just hear the Nazi's out politically, we have no right to stifle their beliefs." Then, you have everyone that refuses to show up classified a bigot against foreign causes and ostracized.
"Muslims will save American Women." Not only can you not call this out, you have such a mass of psychotic assholes behind it, that calling out this fucktarded idea could get you fired, thrown in jail, or killed.
Silencing does not make you correct, or even honest. It makes you the middle manager in a retail store telling people to do shit that's going to get ruined the moment reality knocks on the door. In some cases, it even weakens everything outright, or directly puts people in danger.
"I'm a great drunk driver!" -that's fucktarded, stop DUI-ing you dumb shit.
"Psh, AIDS isn't real, it's just a conspiracy theory." -that's fucktarded, enjoy your AIDS.
Freedom of speech should be free, as it states, because most opinions are terrible and can be ignored. You are making the worst of the worst completely, unreasonably unfuck-withable, granting them immunity to reality at the cost of sanity and safety.
Get fucked.