Argentinian striker Luciano Becchio was flattened by Ashbee's challenge late in the second half after team-mate John Bostock had already been dismissed for two yellow card offences.
Grayson said of the elbowing incident: "I've seen it and it's not too clever. He's got a bump above his eye. But it's not for me to decide. I've seen it and made my feelings clear and it's up to the referee to decide.
"Someone asked me the question on Monday and I've always agreed with what (Stoke manager) Tony Pulis had to say - referees should come out and be accountable for decisions, good or bad, and do a press conference afterwards.
"It shouldn't be me explaining why the situation didn't get sorted when it should have done."
Source: PA