@miyako19 Never said he did it due to religion. Mt Hiei was home to powerful and independent monks. Then these monks decided to
join the war and side with Oda's enemies. They asked for it really. The civilians? Maybe a "necessary sacrifice" to ensure that no monks escape. I mean how hard would it be for a monk to pretend to be a civillian (men or women)? And children would just seek revenge in the future/suffer needlessly without parents. Simpler to just off them all.
There is also another theory that Mitsuhide betrayed Nobunaga because his fief was going to Ranmaru.
Nobunaga's brother betraying him wouldn't mean anything because there is always a "succession crisis" regardless of what country it is. Take a look at the Yuan Family from Three Kingdoms for example. They certainly didn't kill each other while Cao Cao watch and laugh because one of them thought the other was evil. They simply wanted power.
Nobunaga being a progressive person didn't help matters in inspiring loyalty.
Again, I am not saying that Nobunaga is 100% a good person but simply that it is possible he was actually a "good person" instead of "Rawr, For the Evulz!" I am just pointing out possible 'not evil' alternative reasons for his supposedly evil deeds.
Its like saying "Nobunaga is so evil. He burned down Mt Hiei" without saying "Those monks are so evil. (or stupid. Your choice.) They purposely provoked Nobunaga to burn down Mt Hiei."