I'm not sure John McAfee is a valid reputable source for anything computing-related anymore. Not only has he been out of the industry for years, but there is that whole 'delusional on an exotic island under the influence of bath salts, accused of at least one murder, and insisted he was the target of a drug cartel in spite of there being no evidence to the contrary' back-story.
The man does not have both oars in the water.
As for the fellow at Symantec, if they believe anti-virus software doesn't work? Why are they still selling it? This one statement has now wondering about the moral compass of this company and its employees. Of course, AV software is not as effective as it once was as threats have evolved and it takes more than just a good AV to be secure these days. This is why Defense in Depth and Defense in Layers has come into being.
Computers and networks are becoming more difficult to defend. No one can dispute this. It's just a lot harder than just slapping the first AV you download onto the PC and calling it a day. Not only does the AV have to be good, but the anti-malware as well. While you're at it, you need a good firewall that will monitor (and optionally block) anything outgoing as well as incoming. Those are just the basics. There's more than can (and should) be done.
Maybe Symantec's just upset that glossy ads no longer guarantee a fat bottom line anymore? For one thing, glossy ads are almost a thing of the past as physical magazine sales dwindle. For another, consumers are getting smarter and not mindlessly buying whatever trialware was bundled with their new PC any longer. Symantec's never been ones for innovation. Their strong suit is more along the lines of buying other companies and sucking the life out of the acquired product lines. They are the productivity version of Electronic Arts.