This absolutism is unnecessary. Plenty of modern democratic countries have limits on acceptable speech (France, Sweden to give you a couple examples) and they are not less democratic than the US (I would argue they are more).

Limiting speech within agreed boundaries is not problematic as long as it's a decision taken with a good criteria and with a good goal in mind. It's no different than any other decision we make on how we setup society.

What is or isn't acceptable at the time is largely a matter of fashion and opinions. As an example, have a look at the ALA's compiled list of banned books (some of which are banned for ridiculous reasons): http://www.ala.org/advocacy/sites/ala.org.advocacy/files/con...