Welcome to cyclechat Sister Jeanne
Sorry to hear you had such an unpleasant experience at the 'checkpoint'. this must have really spoiled your plans and has obviously played on your mind since.
TBH perhaps you were a bit optimistic expecting to pass the closure signs despite the well publicised and signposted closure and being met and challenged by representatives of the closure authority? It might have played out better if you had approached with the mindset that you would likely be turned back but would try anyway just on the off chance, rather than assuming you would be allowed to continue as 'you were just a cyclist' and then being upset when entry was (rightly?) refused.
What were your actual plans for the ride, to the summit and back, to the roadworks and back or see if you could get all the way through to Ladybower? Did you explain your plans to the people that stopped you, they may have been amiable to allowing you to ride to the summit and back, but then again, they may have had dozens/hundreds of riders agree to turn back at the summit and then in reality continue to and through the worksite, hence a 100% no entry policy?
To be fair, they have to treat every rider as a dangerous halfwit and a liar because it is impossible for them to tell if you are so incompetent that you are going to ride into a hole or collide with heavy machinery, or a liar planning to ride through the roadworks.
There are plenty of alternative great rides in the area so don't feel too bad about missing out on the snake, it is still a great road to ride even when open to vehicles IME. Maybe try heading up the Old Glossop Road to Crowden and climb Holme Moss which is also a great climb/descent.
