Gmail encourages users to reduce PC's security

This has got to be one of the strangest error messages I've ever come across. I was using Gmail the other day and the page didn't load correctly. I then noticed this error message that suggested I disable my firewall software.

For windows users that are struggling against all sorts of security vulnerabilities this seems like a very irresponsible thing to say. Furthermore, I simply can't understand why a web mail service would require my firewall to be disabled.