Vettel plunged his Red Bull team into a huge controversy at Sepang on Sunday when he ignored a pitwall order to hold position and instead overtook team-mate Mark Webber to triumph.
Although Vettel apologised to the team and Webber for what happened - claiming his actions in defying orders were 'not deliberate' – Horner says he is not convinced.
When asked why the team did not ask Vettel to relinquish the position to Webber in the closing stages to make up for his defiance, Horner said: "Do you honestly think that if we had told him slow down and give the place back, he would have given it back?
"There was no point. He had made it quite clear what his intention was by making the move. He knew what the communication was. He had had the communication. He chose to ignore it.
"He put his interest beyond what the team's position was. He was focused on those eight points difference between second and first place – which was wrong. He has accepted it was wrong."
Horner said that the order for Webber and Vettel to hold station was given once they had settled into position after their final stops on lap 43.
The decision was justified because the team was worried letting them race to the flag risked severe tyre degradation problems.
"Following cars very closely destroys tyres," said Horner. "We know we have been marginal all weekend on tyres and what we didn't want to do is run out of tyres and take an unnecessary risk.
"From a team's point of view, we are trying to manage the race from that final stop to the end of the race.
"At this point of the season it made sense to bank the 43 points. All you are doing to allow the two to race from a team perspective is to take unnecessary risk at this stage of the championship.
"Obviously Sebastian chose that he wanted those eight points and chose to take things into his own hands. He has apologised to his team for that and has apologised to Mark for that, and that is it."
Horner said the matter was discussed at length in the post-race team debrief and he hoped the outfit could move on.
"We spoke to both drivers, and I have spoken to both drivers, and Sebastian has apologised to both Mark and the team," said Horner. "So we have conducted our debrief as we would usually do and we will focus on the next race."