It's the riding and the fact that EVERYTHING is wolfy. Being accompanied by wolves in battle? Fine, okay. Heck, the Rune Priest in my game has a Fenrisian wolf familiar. Wearing some wolf skins. Yeah, all right. Having practically everything be wolf this and wolf that? I don't like it. I mean, Blood Angels get a pass because not everything is blood this and blood that. The Wolves are really the only ones that do it, and I'd rather have space Viking berserkers that have a wolf theme than Space Furries that Wolf the Wolf Wolf, if you'll pardon the term.
That, and riding a giant wolf is just plain silly.