Iron Golems that are trying to attack a player are unable to do so.
They will just try to ram the player and swing their arms, but the player doesn't take any damage.

To reproduce:
Find a village that has an Iron Golem. The player should have no prior reputation in that village, or at least no positive reputation (from trading).
Now attack or kill a villager so that the player's reputation gets negative or punch the Golem. The Iron Golem starts to attack the player. Observe how it tries to hit the player, but is unable to do any damage.