This is very dangerous to blindly and thoughtlessly disable basic security features of operating system. Would be very ridiculous if Apple Support recommended doing so every now and then. I hope, that was just a figure of speech. Both firewall and Gatekeeper weren't developed just for fun, wasting whole lot of time, efforts and Apple engineers' salaries for nothing. Do you think that one day Apple executives would exclaim: let's make everyone's users' life just trickier! And then they'd laugh like in Dr. Evil movie. And then there would be a Nice Man who'd save the world and tell everyone just to disable it. How can you be sure you are not a target for a MITM fake update attack? Think twice before disabling anything in your system just because some guy in the Internet told so. And if you really need it, never forget to turn it back on as soon as it's possible after completing your task.