But PGP comes with private cryptosystems implemented, thus even though public key cryptography is used to transfer the secret keys for the private key encryption, the software still contains what could be termed munitions (assuming you are correct to call all public key cryptography in the public literature as snake oil).
Public key cryptography is a type of encryption that uses public keys or public key exchange. Mostly it uses some form of the Diffie-Helman algorithm.
Private key cryptography is based on keys that are not exchanged publicly, and must be transferred by secure channels, either physical or encrypted electronic exchange.
I had the impression that at this point of time, with suitable keys, it is impossible in practice to break the stronger variants of public key cryptography, even with the computational capability of certain government agencies, unless their mathematicians and cryptanalysts have proved otherwise.
DH key exchange does not use secure channels, it uses 'public' key exchange. Its security relies on the fact that it is computationally difficult to calculate the key using only the transferred information. Difficult but not impossible. Secure enough for your meatball recipes and credit card information, but not enough for information that could cause harm of an extremely grave nature.