Only way of fixing that works, is mcediting (removing all nearby entities). Might take a try or 2. Be aware that this method removes any other mob as well, including friendly ones.
The worst part about the pigmen getting angry is that they can become angry without necessarily attacking them directly. Killing something, which attacked a pigmen will aggro them. If they're killed by another fam they'll chase you down as well.
Seems like the pigman are seriously broken... Locked my game on hard, so these pigman are making the game unplayable. They're massing around my portals now lost quite some gear because of them...
Hmm, did not check most of the more recent snapshots, but it seems like it doesn't happen anymore. I checked out the spot a few times in 1.7.5 and 14w10c. I couldn't find it listed among the resolved bugs. So it seems like it was resolved unknowingly?
Should I change it's status into resolved for now?
I can confirm this for version 14w04a
Should I consider this issue fixed? Snow layers still generates on packed ice in some rare spots, but unlike before clearing one snow layer no longer causes the snow layers on top of adjacent packed ice to pop off. However if generation of snow layers on top of packed ice is not intended, the issue could be left open, though I'd have to update the description. This is in version 1.8.3