I think Karl and the Kings must realize more and more, that character counts. When your two best players don't lead by example, others will certainly follow.
Unless you're referring to Rondo and Gay, I'm not sure that this is fair. How is Cousins not leading by example? He scores, he rebounds, he passes, and he's played really good defense on a team when nobody else outside of WCS does.
Maybe we're watching a different team, because is frequently the last one back on defense and he constantly whines and complains to referees. He's as talented as they come, and he's all the things you said above when he's engaged. But it's not nearly enough to consider him a guy who leads by example.
I know Rondo has a reputation around these parts, but he's been the leader of that team for better or worse.