It's because there's no situation in which you (I hope) or I could conceivably be accused of being child pornographers. It will never affect us and the people it does affect are the worst of the worst and are identified as such by police.

I have mild conservative sympathies and get accused by idiots of being a "Nazi" depressingly frequently. It's screamingly obvious that the rush to clamp down on "hate speech" is in reality criminalising political dissent. Which is absolutely guaranteed to lead to more violence, not less.