This is still a problem in Minecraft 1.14.3 Pre-Release 1
This is still a problem in 1.14.2 pre-release 4
(To everyone saying that you can put the game in peaceful mode, yes. you can also kill all zombie pigmen entities. But if you have a farm, like a gold farm, you rely on named zombie pigmen, and if you go to peaceful, they will disappear)
This is still a thing in 1.14.2 pre-release 2
This seems to still be the case in 1.14.1 release.
Can confirm that the aggro problem is fixed in 1.14.3 pre 2