Just doing a bit of Doctor Who related derping on the internets, and oh my God, I cannot believe I didn't notice this before (having seen the Classic story in question)

So was reading something about Genesis of the Daleks (one of the Fourth Doctor stories) in which the Doctor is sent back to Skaro to alter the creation of the Daleks so that their progress would be slowed down or kill the creatures before they fully emerged, because there existed a possible future where the Daleks would destroy the Time Lords and dominate the universe. In the end, the Doctor could not bring himself to destroy a species for sins that had not been committed. He chose instead to simply slow down their progress, because he believed some good still came out of all their evil, that alliances and peace treaties were formed between other races because of the shared fear of the monsters.

So essentially the reason the Doctor feels so guilty about the Time War is that he thinks it's partly his fault that it happened in the first place! If he had done what the Timelords had asked, it would never have happened! And in interfering right at the beginning, it's what made the Daleks hate him and the Timelords so much in the first place, and possibly what made them decide to launch a full scale Time War against them...

Why did I not notice this the first time I watched it (which was after the new series started, so I knew about the Time War...)?!