Fonte had cancelled out Jamie Peters' 19th minute opening goal.
Both Keane and opposite number Neil Warnock agreed the dismissal was harsh and proved to be the turning point in the game which was settled by second-half strikes from Palace duo Neil Danns and Victor Moses.
Keane will review footage of the incident before deciding whether to lodge an appeal against the decision.
But the Ipswich manager was incensed at the way the Palace players reacted by crowding around referee Paul Taylor immediately after Stead's mis-timed tackle.
"I'm still amazed when people seem to enjoy seeing players get sent off," said Keane.
"Some players get involved when they should have nothing to do with it.
"Other players, other managers, trying to get players sent off. It's ridiculous. That's the horrible side of football.
"It's up to the official but officials are put under pressure in different ways - but when players are sprinting up to the referee trying to get a fellow pro sent off?
"They're all supposed to be in a union together, they'll no doubt be at a dinner together at the end of the season.
"But I'll have nothing to do with it. I never want to see other players get sent off, even if there were a few tackles going in on our lads - unless there's something obviously over the top the player's going to get a red card.
"But know your players, Jon Stead's not that type of player. It was a typical striker's tackle. But let's not talk all day about the tackle.
"That happened and the decision went against us, but we still have to react and that's what we didn't do."
Warnock shared Keane's view that Stead had been hard done by, but insisted his side fully deserved the victory that keeps them in sight of the play-off zone and ended Ipswich's 10-game unbeaten run.
"I didn't think it was a red card," the Palace manager said.
"I expected it to be red, but I didn't think it would be red.
"You could see he was disappointed at missing out on the challenge before, but I know Jonathan Stead and so does Roy."
Warnock added: "We could have had more goals. I thought their keeper was the busiest goalkeeper, even before the sending off I thought we had more opportunities, but the goal gave them confidence."