Everyone is free to give his opinion. In your above-mentioned article, McAfee didn't gave any logic that can support his prediction. Based on such news one shouldn't start buying. Bull run is on the cards and we must remain prepare for it all the time.
And this is why some opinions remain as a opinion. Its up to you if you will believe to anyone but for me I know that bull market will always come after a big dump its just a matter of time before it happen so basically patience is the key here.