The fact it was clearly never a red card for Calde is exactly why the club should appeal. If it doesn't get overturned what the hell is the point in an appeal process? Referee cocks up, video evidence supports this, FA say the penalty stands plus an extra game for daring to appeal. Referee...
That's how I see it. If anything, their player slides in with studs showing which, these days, frequently means a red card.
I think that w@nker Edinburgh may have helped get Calde that card.