Rather than saying nope and ignoring the request only causes the contributor to not contribute again . If you could only explain why it should not be done.
Also this is one of the main reason why people don't contribute to open Source. Rather than ridicule them , tell them what they should do better.
With all these NSA revelations and Richard Stallman being right all along. there is no such thing as being secure or encrypted unless you have encrypted it yourself.
It could be like leaving your bank account password in the open.
Your bank account password could be sniffed probably very easily by someone who is connected to your network. Now imagine somebody exposes some way to get the password of your home network from the google servers.