Attacking a wandering trader near a village with an iron golem will not anger the golem, despite the trader itself being a villager-like mob. I have tested this multiple times by attacking/killing wandering traders near a naturally-spawned golem.

How to reproduce

1. Get a wandering trader spawn egg (stack of 64)
2. Attack the wandering trader
3. Notice the iron golem is not doing anything to defend the wandering trader from the player.