On my first day as a PM leading a team of 5 developers, I had a meeting with the Marketing director as I was brand new to the company. She welcomed me by telling me: "Your developers are total idiots who don't understand anything to the business" while smiling to their faces which has marked me forever. What I learnt from that experience is you can't reason an asshole (I tried too many times over and always failed), if this asshole happen to be your main stakeholder and you can't change that, then get another project or step aside.