I can't say that I blame the Ukrainians for maiming captured Russian soldiers.
Were the same to happen in the US (queue Red Dawn), I rather doubt US forces, fighting a defensive war on our home turf, would give a sh!t about POW rules.
I acknowledge the difference between uniformed regular forces fighting an urban guerrilla insurgency versus irregular civilians, but I also suspect that at this point the Ukraine resistance is heavily bolstered by irregular forces who are not technically protected by Hague Conventions anyways. Once they start fighting, they're not protected by them, so treatment of POW's doesn't matter, and they probably know fellow countrymen and women who have been kidnapped from Ukraine and taken into Russia (since Russia has been pulling that sh!t in the last week or two). Kill them, hurt them, maim them, demoralize them, shame them, terrorize them. Do whatever it takes to make them fear coming to your country more than the repercussions of disobedience back at home.