You can attack the iron golems with the Buck-Chuckets on the live event and do damage. It affected me and I play on Windows.
MCPE-208090
You can kill the iron golems at the outer walls on A Minecraft Movie Live Event
Open
2
Due to the event being nearly up this bug report may be ignored. Especially since this is an event promoted by mojang but was hosted and created by sparks universe, so I'd suggest contacting them instead of on here. However the event itself was very buggy on its own.