Freedom of speech is important not just because it is a basic human right, but because it is necessary for societal progress. Freedom of speech and expression is what provides society with new ideas, theories, opinions and beliefs. Without these new insights, society cannot progress.
Take the example of Galileo, who was one of the first people to push forth the idea of heliocentrism. Now, at the time he published his works on heliocentrism, it was met with disdain and criticism because it was supposedly offensive to Christians and Christianity to suggest that the Earth was not the immovable centre of the Universe. So, the church barred him from publishing his research and expressing his ideas, essentially suppressing his freedom of speech. But now, centuries later, we realise that the Church was wrong. Galileo was in fact right about how the world works.
The point here is that no one's thoughts or ideas should be suppressed simply because they are offensive or inappropriate. It was because of this suppression that Galileo did not receive the recognition he deserved until much later. More importantly, it prevented us from knowing an important fact about the world we live in. The same can be said for modern ideas and opinions. If we suppress peoples' ideas, we'll never discover new things and attain new insights and will simply be forever stuck with the same ideas, hindering societal progress. Thus I am for freedom of speech.