The right of free speech includes the right to offend, and it includes the right to defend.
If someone wants to say something horrific, let them. But it's in the public domain, and it allows those who are offended to state why that person is wrong. Banning such things from being said then allows the original person to cry persecution, and leads others to think why can't it be discussed in a public forum so that people can understand what they said was wrong and disgusting. It gives a chance for all sides to put their case forward, and for the wider audience to understand the situation.
But banning things just leads to the abuse of power, and in the end that's what festers strong feelings without recourse for education or for people to be told why they believe such and such a thing is wrong. That's what breeds terrorism, that's what breeds underground movements, that's what breeds people to go out at night and target sectors of the public.