How do you spawn mobs aggressive towards iron golems?

I am attempting to create an arena for my sick tastes of entertainment in which an Iron Golem must survive endless waves of mobs. This would be a simple matter, except that the mobs only become aggressive towards the Golem once they've been hit. It's not that exciting to see a golem walking around casually attacking mobs who don't have time to see what hit them. Is there any way to spawn mobs, preferably using the /summon command, that are automatically agressive towards any nearby iron golems?

Solution 1:

Put a villager in there. If the mobs attack the villager that Golem might go nuts trying to protect it. Tho I'll admit I'm not sure beyond that. However I know from experience that Zombs will attack Villagers and that Golems will protect them.