You know, I've seen lots of different and weird hates thrown around by anime fans.
Fan wars, Versus battles, ship vs ship, etc. It happens. It's a weird part of the love. (Until it's too much.)
With that being said, though, I can honestly say that I almost never find any Rukia haters. Maybe an IchiHime shipper here or there, but otherwise, nada.
There are reasons for that.
Rukia Kuchiki is a badass.
Rukia is the first Shinigami that we are ever really introduced to in Bleach. She is the reason for Ichigo even become a substitute Shinigami. She has been at the center of her own arc and she has been a loyal friend to Ichigo since the start.
Her own innate abilities are nothing to wag a finger at. She is a competent Kidou user as well as an expert swordsman. She has kept toe-to-toe with some of the strongest opponents encountered throughout the plot of Bleach.
Her bankai is one of the most devastatingly impressive feats displayed by a member of the Seireitei. She is able to immediately reduce everything around her to a point of absolute zero. The technique is so powerful, she put herself at risk when she uses it.
She is badass enough to be able to distance herself from LIFE ITSELF to overcome the power of an opposing Sternritter. Who she then killed. In marvelous fashion.
She's who Mikasa dreams of being.
Or if she isn't, she should be.