First off, Nate won't give two shits about fighting at 155 since that's where he has fought the majority of his career. Second, 170 might look like a natural weight but it's not Conor's natural fighting weight. It's extremely difficult to go up weight and have an extended fight. Going up 25 pounds for a fight wrecks havoc on your body's endurance - imagine fighting with a weight jacket on. There's a reason Conor faded so hard in the first fight and ran in the second to conserve energy. Thirdly, he calls the shots because he's the money maker - you should actually respect Conor for what he did. He could have easily demanded for the fight to be at 155 but he wanted to prove to himself and the world that he could avenge himself on the exact same fight terms. Now he is most likely going to have to reform his body over the next 6 months and defend his FW belt at 145 or take a title fight at 155. To expect him to come back again to 170 for the 3rd fight with Nate after another year of fighting at lower weights would be ridiculous. And again, Diaz will not care.
There's a certain irony that you defend Diaz with such vigor, but anyone who comes to you with level-headed arguments is "ball deep" in Conor.