Pony Shield-Doesn’t work very well when death is cheap, you have cortical backups, and you can be back on your hooves in a few days after they pull your cortical stack. This means that taking hostages isn’t a valid option. Of course, threatening to smash the cortical stacks works as a valid threat, but not as a valid shield against attacks.
Also, actually carrying through with killing hostages, even if they’re re-sleeved, is a premeditated murder charge in just about every nation. Done often by Changeling queens and empresses, whom use their captured food sources as a defense against hostile fleets just nuking them from orbit. All this means is that they have to send in the ground troops to get the hostages out. Then nuke them from orbit.