The visitors struggled to make an impact in attack and were punished after the hour mark when Chris Dagnall struck twice in quick succession - the first coming from the penalty spot.
Warnock said after being booed by the travelling support: "We were very poor in the first half and if I had have been one of the 5,000 I might have said what they were.
"I thought we had some great chances at the start of the second half and then there was a horrendous tackle from (Stephen) Dawson. How that's not a red card I don't know.
"You can't blame the fans... they pay their money. But I think I'm doing a great job if I'm honest and with one or two additions that I've got lined up... I understand their disappointment but we know we need to strengthen."
On the future of leading scorer Luciano Becchio, who is the subject of transfer speculation, Warnock added: "His head wasn't right and that's why the transfer window is such a nightmare for managers. I'll be having a word with him."