We didn't 'accept his actions' but instead he told us upfront that he was partial to working in certain languages and frameworks. We mulled it over before agreeing and coulnd't be happier. He is great because he is great to work with, highly productive, self motivated, and brilliant. Sure, I could have hired a dev that only did the exact same things as me, but I might be tempted to get into the weeds more than I probably should. You defining 'his actions' as destroying business value is a poor mischaracterization as he has created enormous amounts of business value. Couldn't be happier with our decision on this.