The spring tension that maintains the force of the wiper against the glass is what is keeping your wiper stuck to the wiper arm stud. As mentioned, fold your wiper away from the glass as if you were washing the windshield.
Once the wiper is folded away 90 degrees it will go into a neutral spring tension position and stay there. At that point, it will lift right of the wiper shaft.
When I replaced the circular gasket around my wiper arm, I ordered the replacement from Winnebago parts thinking it was some specialty item. It turns out that the replacement was a simple thin black neoprene washer. 2 of them were under a buck, but you might just be able to make something or find it locally to avoid shipping. If you do end up ordering them...get several as they don't last long and it will save the shipping.
Finally just a caution....don't overtighten the acorn nut that holds the wiper arm on the shaft....when the threaded shaft bottoms out in the nut, it can twist off....don't ask how I know that
Winneabago has that item too for a couple dollars.
Joe & Shelly, Justin, Tyler, Alyssa | Butler PA
2008 Tiffin Allegro Bus 43QRP|Cummins 425|Honda CRV