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.
They could have also starved him out. Novel solutions to extreme solutions are often cover stories for the introduction of unwanted techniques. After all, who can argue that the bastard needed killing - this time? But then afterwards, we are left with precedent.
Slippery slope indeed.