At geosynchronous altitude there aren't enough satellites or varied orbits to create an impassable debris field. Consider that the sphere surrounding Earth at an altitude of 36,000 km is huge. Deconstructing every geosynchronous satellite (including graveyard orbits) and spreading them across this area in varied orbits would not even begin to constitute an impassable barrier. Add to this the fact that most satellites at this altitude reside at 0 degree inclination and the resulting debris would in reality occupy an equatorial band.
I'm not even sure that a Kessler syndrome type scenario at LEO would pose much of an issue for deep space travel. Some orbits would be especially dangerous, but the average debris field would still be sparse.
Photos such as the one below (ripped from wikipedia) make it seem like a debris field would be impassible only because they magnify the size of the mapped objects (otherwise you wouldn't see anything):
The main danger of these scenarios is they make orbits unusable until the debris are removed or their orbits decay. For GEO, the time for orbits to decay is essentially forever (as far as we are concerned). Unless I am mistaken (and if I am someone please tell me why), the idea of a Kessler syndrome event preventing deep space travel is mostly hype.