QPR's relegation was confirmed on Sunday after a goalless draw at the Madejski Stadium, with the Royals also dropping down to the Championship.
Television footage showed Bosingwa laughing as he made his way towards the players' tunnel after the final whistle, but Redknapp has defended his player.
"He wasn't laughing about the result or getting relegated," said Redknapp.
"To start throwing that one about is completely out of order. He was only laughing because one of their players - another foreign lad - came up and said something to him."
Bosingwa was criticised by fans on Twitter after the match and midfielder Joey Barton, on loan at Marseille from QPR, also felt his behaviour was inappropriate.
"I can't believe QPR have just been relegated and Boswinga was walking down the tunnel laughing,' said Barton on Twitter.
"Embarrassing. Show some guts man."
Barton added: "Some good lads but not enough. Too many maggots. Hope they can get a load out."