I watch on Sky over here in NZ. I've watched every replay I can find and can't see how they could blame Karthikeyan. Vettel turned in on him before he had cleared him and the Sky commentary team all saw it that way. It's up to the overtaking driver to give the other driver room and complete the pass cleanly. That rule has always applied to all forms of motorsport. Don't forget, the stewards don't always get it right. Worse than the incident itself was Vettels response to it. Some have said it was heat of the moment, it didn't appear that way to me. He made the comment some time afterwards when he had time to calm down a bit and think of what he was saying.
Buttons reaction was far more measured when Vettel took him out at Spa in 2010, and Button at the time was in the running for the title. I sometimes get the impression Vettel feels no other driver has any right to be on the piece of track he wants to drive on. Vettel and Webber at Turkey ring a bell anyone.