I think he meant to say "A good reason to encrypt your archives", not just put a password on them. If you encrypt your archive, even a rar, gmail shouldn't be able to see the contents inside of it.

Another solution is to simply change executable names to .exe.backup or something similar, that way it'll register as a ".backup" extension for most systems and not be blocked simply by name (though this wouldn't necessarily defeat things that actually detect and block binary executables).