Up against an enemy like MEGATRON and his followers, the AUTOBOTS can't afford to be nice. To ARMORHIDE, this fight is about nothing other than total victory, and the only way he sees to achieve that is to become as much like the DECEPTICONS as possible. He knows OPTIMUS PRIME doesn't approve of his methods and he doesn't care. Once the DECEPTICONS are wiped out the historians can argue as long as they'd like about whether his way of fighting this war was right or not, but at least they'll do it in peace and safety.