Pin-pointing a laser onto a moving target is getting progressively more difficult the faster the target is. Targeting optics need to be progressively faster and more precise to hit the object for the time needed to have the intended effect. And all the effect the laser it has is proportional to the energy it deposits per square centimeter onto the target. With more air passing by the object, even more energy is dissipated and with the faster speed, the total flight time in range of the laser is progressively shorter.
That's what makes hypersonic weapons so dangerous. They're too fast for defensive missiles to counter. There's less time for detection and identification overall, less time for a friend-or-foe decision, less time to align the laser spot on the target, the laser will be less accurate on the target, depositing less energy per square centimeter and second, the while the projectile dissipates more energy per second to the air around it and the laser system will have far less time anyway to destroy the incoming projectile before it impacts the thing it was supposed to defend.
Look at the few leaked videos of hypersonic missile impacts. These missiles are so fast that there's barely a 1 or 2 seconds between the missile appearing and impacting. Current lasers have AT BEST a 10km engagement distance and that doesn't include the plasma shield that air forms around the HGV due to air friction at that speeds. At Mach 12 and ideal conditions, the laser will have less than 2 seconds time to deliver all its energy, through all atmospheric distortions, follow the HGV's potentially unpredicable flight path without instantly and permanently blinding all humans near and around the defended area.
Atmospheric dust and smoke will quickly render that even more impossible than it already is. So even if the first few defense shots MIGHT be effective, every subsequent shot will become harder and harder because there will be more and more dust and smoke in the air around the laser. If lasers become too effective in the future, then you will see the attackers firing whatever they can find to increase smoke and dust in the atmosphere around the laser or reengineer their HGVs to release insane amounts of smoke when targeted or destroyed so you can at best destroy the first few of them until there's far too much smoke around to do anything with lasers against the next wave. Or they wait with their attack until there's fog or dense clouds over the target, forcing the defense to use MASER or similar things that could penetrate clouds more easily, but who knows what disadvantages that brings. And the Chinese leveraging their most prominent strengths, you can be absolutely sure their HGVs will be mass-produced in ridiculous numbers and through economies of scale become ridiculously cheap as well. They will then simply spam them over the target so that no amount of laser technology will be able to counter them, because you can't reasonably concentrate the amount of energy needed to defend against all of them. Even if you had 100 or 10000 lasers of the required intensity (1MW or more), there simply won't be enough Watts / Joules around to feed them all.
There is very little defense against mass-produced, reasonably cheap gliders at speeds above Mach 4. The attackers can distribute production and stockpiles of gliders over their entire country and produce and stockpile for years, and mass them on any single target. The Joules needed to produce them can easily be transported to the factories, because there's enough time to do so. The defenders would have to place enough lasers near all potential targets to counter a massed attack on any of them. The Joules needed to fire the defense lasers would need to be transported immediately from everywhere to any one target area or stored everywhere in a way that's currently totally unfathomable to us. And even if we managed to do that, HGV production would profit from these advancements as well, bringing more and cheaper HGVs down on the target, immediately nullifying that advance right away.
In short: defending against cheap(er) mass-produced HGV gliders is literally, physically, theoretically and even ontologically impossible.
If you want to read further, look up "Hobbesian trap", "Fermi paradoxon" and "Dark forest hypothesis".
