I would bet that maybe not, but a disproportionate number of darknet websites is.

P(darknet | child porn) might be low, as you are suggesting, but P(child porn | darknet) >>> P(child porn | clearweb), in orders of magnitude.

My point was, just because there exists one (perfectly valid) objection to Tor, it doesn't mean the project as a whole is negative and should be shut down (what the parent seems to be implying about this email provider).