and the fact that they hold large amounts of CP -- which is the wording the prior post used -- is also verifiable fact.

I'm not even concerned that they hold it. Sometimes it's evidence. Sometimes it can be used to identify and rescue victims. Sometimes it just goes in a database and isn't ever accessed again. Meh.

The continued distribution is concerning, though I understand its purpose, and I presume there are reasonable safeguards in place such that the value in catching new suspects is higher than the harm done to the victims.

The only example I'm aware of, regarding your claim about the FBI operating a site for months, was not in fact the FBI continuing to operate a CP site. In that instance, they kept allowing attempts at signing up to access CP, they did not keep allowing access to the content; the FBI clarified that point when the story came out.