Gardyne scored a minute from time to earn United a 1-1 draw against their rivals on Sunday at Tannadice, in a match where four Dundee players were booked and one dismissed.
Dark Blues defender Gary Irvine, who escaped an early sanction for a reckless lunge on Gary Mackay-Steven, received a red card for going through Richie Ryan in an aerial joust after 20 minutes.
But Gardyne reckons Irvine, who he played with at Celtic, and his Dundee team-mates have only adopted a ruthless approach under Dens Park boss John Brown.
Gardyne said: "The manager has obviously brought that to them.
"I played with Irvine and he was never a dirty player. But in the last derby he was taking bodies for fun.
"If that is the way they want to play the game then fair enough. We'll just keep trying to pass the ball.
"I didn't really see the sending-off but I saw the two-footed lunge at the start which was a straight red.
"Mackay-Steven took five hits in the first eight minutes. The ref could have taken action against Irvine early on and it might have calmed it down."