Zombie Pigmans are Always Mad.
Things i tried:
Getting Killed by Pigmans
Killing Pigmans
Running so far away they dispawn/ The Aggro Timer runs out.
Problem started when i first got into the Nether, Zombie Pigmans instantly started hating me.
Only Spawn area Pigman seem to have Aggro
Thanks for the report; however this is a duplicate of MC-148600.