Note that the URL in the one-liner references the master branch, which can be updated at will by jtwaleson. A much better idea would be to use a link to a specific version if you are going to make claims towards its cleanliness:
curl -O https://raw.github.com/jtwaleson/decrypt/f004b7eab7b949a55ea3c784fb9bac244aa0296e/decrypt.py; chmod +x decrypt.py; ls -la | ./decrypt.py
Even that might not work if he has two versions with the same hash and sends github a forced update with push -f. though that's still a much more difficult proposition than just updating the master branch.
If he can generate two files with the same hash he can do much more interesting things than write a sketchy python script that a few people might run without reading.
