Rangers striker Alfredo Morelos "conned" referee Craig Thomson, said Motherwell manager Stephen Robinson after his side's 7-1 defeat at Ibrox.
Carl McHugh received his second yellow card for handball in the box, though Robinson called his first booking for a foul on Morelos "a disgrace".
However, he also accused his side of using the referee as an "excuse" in the thumping defeat.
"The first booking is a disgrace, it's embarrassing," said Robinson.
"And I have to say, referees are getting conned by the same people continually. Certain players get away with certain things every week. They (referees) have a hard task.
"If you are getting fooled every week then it's difficult for them. It wasn't a free-kick in the first place, it certainly wasn't a yellow card."
Scott Arfield had given Rangers an early lead, but Curtis Main drew Motherwell level.
McHugh was then penalised further when he blocked Andy Halliday's shot with his arm and Robinson was sent to the stand by Thomson for his protests.
After McHugh's dismissal, James Tavernier scored the resultant penalty, followed by goals from Morelos, a second for Arfield, Glenn Middleton and an Eros Grezda double.
Robinson said: "I think some of the boys used the referee as an excuse. Let's be very frank here, we were very poor defensively. We're not going to blame the referee.
"I've protected a lot of these players, stuck by them and been very loyal and I didn't get a lot back today."
On his own dismissal, Robinson said he felt hard done by.
"Listen, members of their staff came up to voice their opinion," he added. "I was the only one sent to the stand.
"A young boy, out of his depth as a fourth official (Craig Napier), obviously he can't deal with that. I don't think it was a major incident."