Nobody argues with that. It's the precedent for the weapon that is concerning. Specifically, in using it elsewhere, under conditions where it is not immediately and absolutely required. Cops get killed under all sorts of conditions. So the next step is a drone bomb, right? What about never seeing any human cops again - just drones. Don't want that? Why not - you want cops to get killed? So where's the argument against it?
They already have guns mounted on robotic entrance so a grenade is not a stretch.
It all comes down to policy.
I'm not thrilled with the concept personally because the prime justification for such a device is to resolve hostage situations while protecting the hostages and general public and an explosive device is not the best hostage rescue option for obvious reasons.
The issue is when society spins out of control and violence becomes the norm, such tools become a justifiable slippery slope kind of necessity.
My personal preference is to have a peaceful and tranquil enough society where a old school revolver is maore than adequete side arm for LEOs.