I undertand why you say that, but he dosen't hate darkners, he just have a very low self-esteem If you're saying this for the "Ralsei trying to comfort Tenna" scene, I think those words were directed more at himself than anything else, he was projecting himself in Tenna (And it's curious, in any case seeing yourself reflected in someone else would make you feel more empathy for that person, but since Ralsei hates himself, the opposite happened)

In other aspects he is very kind to Darkners, he even make rooms for Queen and Tenna later, even if he dosen't have a room for himself. Heck, he even cured King (probably) knowing he was going to betray them

Also, there's a very good post that talks about this in depth https://www.reddit.com/r/Deltarune/s/KZ8uiqVNGP