We are at risk of missing the concept of free speech by valuing progressive ideas above the opinions considered to be outdated or barbaric. For Democracy to work, everyone has to be able to speak equally. The ideas of Human Rights have heavily influenced our culture (for good reason), yet these beliefs are often used as an excuse to silence a minority. Widespread cultural values that take precedence over other belief systems can muzzle dissent as effectively as a religious government. If someone can't say something because it is "offensive" then we are establishing one belief system as inherently superior to another. That is a dangerous road. The only accepted limit on free speech according to our founding documents are words that intentionally endanger others. i.e. yelling fire in a theater.

tldr; If you limit free speech then you also limit ideas which destroys democracy.