But here, there's no downfall of humanity just a profecy that's not yet confirmed. That's why red dragon is anxious. As shown in Ch3, where he's becoming desperate, since he's waiting a lot of time. Also, you can't also justify the death of innocent dragons, such as the white dragon. In the story there's no telling dragons are evil beings, just that they were the enemy of humans. And who but the royal family could sent the knight to kill them all? The knight herself told Mc that he has no choice since she was a knight and it was her duty. Ch 2 and 3 shows that she has to obey and even die without fighting the king, even if he was to take her daughther away. And abou that evidence, it's all in the way he treats and care for Mc. He asks nanny in ch 4 how to treat her, and in ch 6 the expressions he makes for her tells you all. Why would you make a face like that for a mere human? If you want to die by her hands, there's no need for kindness, even if the sword needs a pure heart, Mc won't change its pure heart as she is the Main character. And in the Ch 2 and 3, he said himself why he killed the queens, and the empress said the same to him. He wanted to give knight a message, and also killing her in front of her daughther was ruthless as f, so why at that moment and not taking the daughther out? For the same reason he was killing the queens, patience for revenge. In ch 4, the nanny herself said he only killed all the royal family, not others, and since he's a dragon, he knew the difference between a nanny and who was in charge or gave orders to others to slay dragons and It was 10 years ago. The same time all the dragons were killed to almost extinction. At the introduction of the story, they told you that after the creation of the sword, all dragons but Mc where all exterminated by the knights and for the hero it took 10 year to kill the last of them (Mc).
I'm not asking everyone to sympathize with the red dragon, just to not insult him, since he has his own reasons for being like that. And also in other stories Mls are like that. Killing innocent people at war, like in the hero's wife. You see the Ml going to war, but doesn't show how many soldiers killed, or how they took food of towns people to feed the soldiers for example. At the story of "the lady of the lamp", the Ml killed her and all her familly, also purged all the citizens after her dead before she reincarnated and reincarnated again. All innocent, not only nobles, and still insisted on killing them all for same reasons when she (Ml) came back in time. You know why it's not a big deal? Because you didn't built and idea for the people who died, they just told you they were in the wrong, and also because the ml was purely human and really carefully brought to you so you could love him more He was appetizing for readers eyes.
And again, Most of the Ml are like that. Like in "the villain saviour", "Why Are You Doing This, Duke?", or "Sincerely: I Became a Duke's Maid", the Ml is doing what it takes in order to get what he wants, even killing, but is still loved and I can also tell other mls and his reasons to doing what they do against innocent people that are between their way and readers don't count them since the author doesn't show it to you