It is in Single player. Difficulty = Hard. Natural Regeneration is off. I can go to the nether. Walk up to pigmen and they are all placid and friendly. Start mining in an area where there are no ghasts or blazes, I know that bug about attacking a mob that hurt a pigman exists (this is different). Suddenly when mining Nether Rack a random pigman who was previously identified as friendly charges in and attacks, of course if I defend myself they all join in, but if I move over 100 blocks away (usually 300) everyone settles down and I am able to repeat the issue.
Having been able to recreate this issue in the 1.8 versions I have played up until 1.8.1 pre release 3, I tried in 1.8.1 pre release 4 and was unable to get a zombie pigman to attack me as I mined netherack and quartz.
Previously, it happened 100%. I do not know if any code was changed, but something has. Either in my game or the code. I started this game in the first 1.8 snapshot and have had some snapshots that caused issues and rolled back. But, I have also accidentally loaded the game with 1.7.10 at times. And did that recently with a 1.7.10 Modded Lord Of The Rings Minecraft. It left a lot of empty chests, which was a pity, but easily repairable. However, if that could affect things I guess I should report it.
But, suddenly things appear normal.