Aramaki not being cut out for politics when he is doing an honest job with his work. Kind of the point that politics can be sketchy in a reality of it.
I can understand Batou’s pain because seeing someone with promise put in a position they weren’t ready for had to hurt. Not to mention looking at the family’s reaction when seeing Batou. No surprise the younger brother is pissed. For both Batou and the younger brother it is easy to think what if. If Yano never joined he would still be alive. If Batou made sure to know what the rest of Section 9 would assign Yano in the mission he could be alive.
But at the end of the day the key in life is to not be fixated on those what if’s and figure out how to push forward.