I never said you endorse it. I said the position which you take has the effect of endorsing it. At the least, the position you appear to support requires a person to ignore this particular crime, or accept it as a necessary consequence. So far you have not explained why this particular feature is something society should accept.

In my opinion saying that there is something so valuable to be preserved that we should countenance the perpetration of a crime to achieve it, is endorsing that crime as a necessary component of the goal. People who endorse due process admit that allowing criminals to escape justice is a necessary feature, and in some sense are endorsing a system where some criminals avoid capture. So are free speech purists endorsing the necessity of a means for conveyance of child porn, so as to facilitate other speech.

That's not the same as saying that free speech purists endorse the porn itself, only the necessity of the freedom to transmit it.

You should have the freedom to transmit it and to face the penalties law imposes.

Free speech does endorse the freedom to commit a crime, but does not endorse the criminal activities themselves.