I have enclosed a village within a line of blocks 1 block off the ground to stop any 2 block tall mobs from getting in, of course this doesn't stop baby zombies who are 1 block tall from getting in on the rare occasion. I then spawned 2 iron golems to protect the town in case, so far I have never witnessed one killing a baby zombie so seeing one in the town I pushed the golem to do the work for me and it completely ignored it, walked into it, then getting attacked by it but still doing nothing. Seeing it was going to die I killed the zombie myself but believe there is an error somewhere here