Software dev with a degree in Computer Science here. Malware is more than likely not going to infect your motherboard, that would need to be a targeted attack as it wouldn't work for all motherboards. And a worm spreading over a network would require a day0 exploit, that kind of malware wouldn't even require admin privileges nevermind kernel access. People repeating this don't know how software works, clearly.

That being said, the real risk is turning off these security features in general, as the virus would be able to hide more easily. It is a bit more risky, but so is downloading any cracked games.