Warnock told Sky Sports News: "[Varney] has put his arms up but he has not actually gone in with his elbow. The contact was made below the chin but the kid has gone down like he has been hit in the head.
"But you don't get those decisions sometimes. I have no complaints with the effort today. I am just disappointed that an experienced referee like that has seen fit to send him off.
"It's getting soft now the game, you want to see some proper sendings off. That is not a sending off. I don't know what the game is coming to."
Defeat at The Den leaves Leeds languishing in 18th place in the Championship table.