Double world champion Vettel lost his cool with Karthikeyan in the aftermath of last month's Malaysian Grand Prix.
Vettel was relegated from fourth to 11th after incurring a puncture to the left-rear tyre on his Red Bull following a collision with Karthikeyan's HRT.
It meant that for the first time in 27 races Vettel finished a grand prix but failed to pick up a point.
The 24-year-old later compared Karthikeyan to an idiot, which prompted the Indian to describe the German as "a cry baby".
Karthikeyan has since insisted it is time to forget about the incident, and has no plans to speak to Vettel next week when Formula One pitches up in China.
Vettel has now claimed his reaction was "part of the sport".
Speaking to German newspaper Sport Bild, he added: "I lost a solid fourth place, so that's obviously disappointing.
"Sometimes you let some emotion show, and I don't think someone should be ashamed about that."