Kevin Gallen's leveller came just a few minutes after ex-Manchester United keeper Culkin flattened Clive Platt - who had opened the scoring in the 44th minute - outside his area.
Referee Phil Joslin only flashed a yellow card at Culkin before Tony Thorpe's through ball at the other end allowed Gallen to coolly preserve Rangers' unbeaten home record.
Posh boss Fry said: "I can't believe the keeper stayed on. If that had been our keeper he would have gone.''
QPR boss Ian Holloway admitted: "Barry is probably right about Culkin being sent off but Curtis Woodhouse should also have gone for a few of his challenges in both halves if that's what he wants to talk about.''
Fry had greeted his side's goal by aiming a two-fingered salute at his own fans who had barracked him throughout the half and even hoisted up a 'Fry Out' flag.