Kiddie porn is free speech. But I cannot imagine a reasonable person believing there is any redeeming social or artistic value in it. So I think the overwhelming majority of people are very supportive of laws sanctioning kiddie pornographers.

So is "free" speech actually open only to that speech which is normative to society?

I think if we let the twisted thoughts breathe a bit we can all list any number of things that we accept as evil without a second thought and applaud absolute suppression of those activities & behaviors. Some taboos are so strong that nobody is willing to take the side in an argument in which they must advocate for those behaviors. Is that rational?