Encryption plugins on top of other mail clients has always been a recipe for disaster.

That being said, why would EFF tell people to completely uninstall it? When I hear that, I think "There is a crazy, in the wild, no user interaction needed remote code execution vulnerability". If someone had a use for PGP/GPG email (assuming they understand the threat model and the metadata that is not encrypted), surely they're better off with a buggy version that with pure cleartext?