Schumaker will now miss this weekend's trip to Scunthorpe.
Talking to the Telegraph & Argus Wetherall said: "I've obviously got to be very careful what I say about it but from my view 30 yards away it was just a 50-50 tackle. We were as likely to get a free-kick as they were.
"I was pretty upset when the referee gave a free-kick against Schuey and absolutely amazed that he then sent him off. It seemed a fairly innocuous incident but the referee must have seen something different to me.
"There seems to be an unwritten rule in football that the second booking has to be a worse foul than the first one. But that certainly wasn't the case.
"Schuey made a couple of rash challenges before that but he's of the opinion he played the ball in the tackle.
"I don't think there's any doubt that it changed the game because we were well on top at the time."
Blackpool boss Simon Grayson said of the incident.
"It was probably a little bit harsh but the referee is there to make decisions. He gets some right and some wrong - we had the same thing when Shaun Barker got sent off at Yeovil last week so I know how David feels."