What if the Blossom server doesn't give a shit about people uploading child pornography? I know that if I ran a Blossom server over Tor I probably wouldn't care what users decided to upload. Any user who enables Blossom over Tor would start seeing any child pornography any other user feels like uploading.
But seriously, besides the ability to host child pornography, what would a Blossom server even get out of operating over Tor?