Lyric discussion by chikenlegg 

Cover art for Old lyrics by Machine Head

The Old Man is the Christian church. Not the devil. Two things give the metaphor away. First, 6000 years is a direct reference to the Young Earth theory, a movement recently pushed by many Evangelical churches. Second, Robb constantly expresses in his lyrics a hate for modern leaders, whether they are the government or the church. Look at the song Death Church and Blood of the Zodiac for the church, and a whole ton of other songs for the government.

I've never heard one song from Machine Head that attacks God or faith, only people and usually leaders.