Am I understanding this wrong? Sounds like he Mankaded him?
Don't see how some mythical 'spirit' comes into this equation. The batsman took an unfair advantage, was warned and then did it again, bang, off go the bails, on his bike. In the vein as the Finn hitting the stumps issue. He got a warning, did it again, dead ball. Too bad, so sad, told you not to do it.
It's tough if he has hard feelings and if I was Karthik I'd tell my captain to stuff off, he certainly isn't apologizing on my behalf.
Not walking is against the spirit, we don't castigate batsmen for doing that. It's funny how any kind of unusual dismissal or dismissal as a result of brain-deadedness is considered against the spirit. As if they don't get enough in their favour as it is.