I reckon what often happens is that the car has, at some stage, dropped a wheel into a pot hole, bottomed out the suspension and slightly bent the top pin. Nothing is noticed until you want to extract the pin.
Your pin looks to be in pretty good shape and given you can rotate it, even better.
Don't have a good answer but I'd try a BF lever between the rear wishbone and the chassis while turning the pin.
A rubber mallet is too soft.
Try a nylon mallet or a steel hammer after moving the nut up to the end so as not to damage the thread. You may get lucky.
These pins are a bit like door hinge pins, I reckon.
We've all seen umpteen threads where people diligently try the good ideas and finally concede defeat and employ a zip disk on an angry grinder.
Way back in the dim dark ages, I recall someone found a suitable length bolt from a Caterpillar tractor of all things – cheap enough, too.
