Again, the reason we are going deep into obito's Thinking and History is because of his role as the anti-naruto.
He parallels naruto which makes everything he does or thinks important to the plot.
If nagato was in the same position and paralleled the main character, He would be spouting nonsense about yahiko the same way obito is.
It's A way for us to get to know the villain and how he thinks compared to our hero naruto.
Obito stated himself that rin wasn't the reason he started the war.
Had Obito's first plan to take the 5 ruling leaders hostage, he would of bargained for naruto and Bee in exchange for the 5 kage Leaders.
War was a last resort for obito.
