This is just one of the many cases of rationalizing one's own mistakes. There's plenty of evidence to back up the fact that warding positively impacts your win rate. Usually the rule goes "if the entire elite of SoloQ and the entire competitive scene do something a certain way, then that way is superior than any of its alternatives unless proven otherwise by those two establishments". Why is Hecarim so good? Because he has a high win rate in top-tier soloQ and competitive games. Don't go about trying to list cooldowns and stats, as that would lead to a complicated web of statistical comparisons that will become entirely irrelevant at the first-next patch. This is similar to warding. Sure you can say "it spots enemies and the reward is bigger than its cost", but how do you know the reward is bigger than its cost? Does it even matter what the reward is? If you can confirm something works well, you should leave it at that and include that in your own games.
So, next time people tell you to "ban <insert non-meta champ> because he's really strong" or "warding won't help us win this game" or any other nonsense, just think of this analysis.
One last thing I would like to share is how I would deal with this. Unless there's a specific reason not to - for instance when someone asking for a ban has already made clear to be a behaviorally disoriented child by screaming mean things in your team's chat - simply ignore it. You can ask people to do something, but you can't teach them to reason properly, or teach them how to play the game. Not much else to do than to sit back and relax.