Johnson was left to rue a fightback from Bradford City which left the visitors floundering in 17th place in League Two but felt the hosts were given a helping hand by a penalty decision from the referee.
"Their first goal has hit Holty in the nose," he told BBC Radio Northampton.
"He's got a bloody nose to prove it. He was trying to show the ref and the linesman. He wouldn't punch himself in the nose.
"When you go away from home you could do without a poor decision like that. That got them back in the game."
Home boss Phil Parkinson felt his side 'got going' after going behind and praised the 'quality' of his forward players after a vital win for the Bantams.