By borrowing the power of the dark camp or the light camp, these people might be the sharpest swords for that camp compared to the original members of one camp alone.
The four demon lords felt that the four archangels were too hypocritical for wanting to 'save' Ainsley from the darkness.
Let's ask her whether she wanted to be saved or not?
For her, the celestials made trouble here and there, and her heart might lean more towards the blood clan who clearly didn't do anything to provoke others.
Even when they needed blood from humans or other creatures, they would always give an equivalent compensation and they wouldn't force those who didn't want to give them blood.
Wasn't it because of this that the blood clan developed their handsome and beautiful faces so their prey could willingly surrender to be their food?
And it was just a little bit of blood, anyway.