Bristol took the lead through Dele Adebola, a former Coventry player, after he poked the ball into the net as goalkeeper Keiren Westwood lay down injured following a collision between the pair.
Coleman felt that his side should have been awarded a free-kick and his frustration was heightened after Clinton Morrison appeared to be pulled back when through on goal and Dowd failed to award a penalty.
Coleman said: "I thought his (Dowd) first-half performance was abysmal. We thought we should have had a free-kick for their first goal.
"Then, I thought it was a penalty on Clinton Morrison. If he doesn't get pulled back then he is going to put the ball in the back of the net.
"We don't get the penalty. I lose my temper and he sends me off. Fair enough, maybe I deserve that for my reaction.
"But it wasn't just one decision, that had been coming and it was decision after decision.
"He won't get a punishment. Referees should be assessed and the poor ones at the end of the season should be demoted. He has had an absolute nightmare and he is going to get away with it."



