Hansson, widely criticised for failing to spot the handball that led to France scoring the decisive goal in the second leg of their play-off against Ireland, was named on Friday among the 30 referees for the tournament in South Africa in June.
"FIFA made the correct decision to put him forward because he is not the person responsible for what happened," Platini told a news conference.
"He didn't see Henry's handball when it happened... although everyone saw it on the television afterwards... and I'm not sure we could identify this as a referee's error.
"He has officiated other games which were very difficult for referees and he did excellently."
Television replays showed Henry twice touched the ball before William Gallas bundled it over the line in extra time to give France a 1-1 draw in the return leg of the November match.
France won the play-off 2-1 on aggregate to reach the finals in South Africa and spark one of the biggest outcries in World Cup history.
Last month, FIFA decided there was no mechanism for punishing Henry for his part in the incident.
Platini said he hoped football's law-making body, the International Football Association Board, would approve the recent experiment in the Europa League, where an extra assistant was placed behind each goal to help the referee.
"Other sports such as basketball and volleyball have made changes, but in football the number of referees has always been the same," he said.
The Frenchman also agreed with world governing body FIFA's inclusion of two referees from New Zealand in the list for the World Cup - more than major nations such as Brazil, Argentina, Germany, England, France and Italy.
"They can be just as good as French and Italian referees, I don't see any reason why they can't go to the World Cup just because they're from New Zealand and Oceania.
"Football is not just about western Europe, it's big all over the world."
