As a CSM I am not trained in weight and balance, and have only a very minor knowledge of it I leave that job to the professionals. I do however have a healthy respect for the flight crew and Captain, knowing that they are trained in this area and have an overall responsibility for the aircraft and its occupants.
I have been asked to move pax once boarded for a number of reasons. The majority of the time it has come directly from the Captain in relation to weight and balance issues (which they have not stated every nuance of). I have then requested the passenger to move and passed on the direct reason to the passenger and apologise for the inconvenience. Most are satisfied with this response.
Other reasons I have asked passengers to move are incorrect seating allocation (incorrect class) or to seat a family or friends together when not allocated together. I have never asked a guest to move to ease the cleaning of the aircraft (nor heard of this) and I find it hard to believe anybody would.
In regard to frog marching a passenger off the aircraft, if they disobey a simple request to move seats due to an operational issue during boarding before the doors are even closed, how are they going to respond to another more urgent request with a few scotches under their belt and no one to call for help besides my small team! You need to appreciate that we are locked in a metal tube with 200+ people with only a few cabin crew to manage and ensure that all safety and security is complied with. If I fear for my own (or crew) safety or that of the aircraft is compromised that person would be taken of the aircraft, but this is a generally extreme response only.
The original post seems to say the CC asked the OP to move in quite a random fashion and when the OP said no, they simply moved on thinking nothing more of it. I do find this hard to believe, as they say there is always three sides to a story, yours, mine and the truth!! I think some (not all!) Flight crew believe all we do is serve drinks and food, then sit down the back and have a gossip. This is like some CC (again not all!) who believe all flight crew do is sit up the front with their newspapers and press a few buttons. This is not an accurate representation of either job and it becomes dangerous when either group starts assuming because they have a little knowledge of either role that they know better and can question simple instructions. What if I as a CSM simply diregarded the Captains instructions to move someone because "what could one person moving make a difference? Hmmmm, I won't bother". Chaos would ensue. What instructions do I then follow and which ones do I not.......
At the end of the day I don't think we will ever know what happened on pd2's flight, as even he stated it was his perception, but I would stress that if CC ask you to move there is a good reason and if you are not happy with the reason provided, ask to speak with the CSM for clarification (which I would be happy to provide). Failing that, by all means make a complaint directly to the airline, if there is a reason other than operational requirements then the airline should know. But to be on the safe side, move........There maybe something that you, as not part of the crew, are not aware....... I am not trained in weight and balance, I simply enforce the directions given to me by those trained in this area and enabled by the airline to delegate these directions to me.
And let's not forget that whenever you buy a seat on an aircraft, one of the conditions is that you will follow all directions of crew, there is no disclaimer that states "but only if you agree with it or don't find it silly!"