At those speeds, even sitting up a little and easing off the pedals should be enough of a deceleration to avoid tangling like Sagan did.No sprinter is anywhere near his brakes during a sprint, they simply cannot reach them without releasing their hold on the handlebars, because they are gripping the bottom of them.
Trying to reach for your brakes in the middle of a sprint is dangerous.
I get that there might have appeared to be a gap on vanAert’s inside, but VanAert didn’t change his line and Sagan apparently decided halfway through overtaking that there wasn’t space at the barrier, so he initiated contact. The result of his contact was to move VanAert a foot or so to the left (and to lose a little speed). If VanAert hadn’t been such a good bike handler, that could have been a disaster. If Sagan had eased off instead of dropping the shoulder once it became clear the gap wasn’t there, then he finishes 4th with no penalty.
And yes, obviously riders like Sagan are always going to go for that gap anyway. Because 4th is nowhere yadda yadda yadda. But it must always be clear that there are limits to that. And going for a gap that isn’t there, and pushing riders aside to make that gap, are things that should not be encouraged.