The upper tiers (no, i don't mean manager, necessarily) of any technical profession basically comprise offering your "opinion", albeit one which is tempered by a lot of experience, logical analysis, and education. Most peoples' delineation of "fact" vs. opinion is, actually, nothing more than a very uninformed opinion.
Linus Torvalds is probably not the best programmer in the world, but his opinions about practical kernel design are rather valuable. It's not a fallacy to act on that.
Finally, the truth or factuality of my statements is independent of whether i convince every schmuck on the internet of them. I simply don't owe everyone that much attention.