Lyric discussion by Efforts 

It's very straightforward.

He's talking to religious people and how they get so much into their religion they are unable to listen to other point of views.

He also attacks God on how it's a hypocrite.

In some traditions, if you are not of Christian faith, you cannot attend the wedding of a Christian couple getting married. The narrator asserts that even though he's not invited to the wedding, he'll be at the wake, when they're dead and nothing matters.

On Bukowski: This is why the song is named so:

"For those who believe in God, most of the big questions are answered. But for those of us who can’t readily accept the God formula, the big answers don’t remain stone-written. We adjust to new conditions and discoveries. We are pliable. Love need not be a command or faith a dictum. I am my own God. We are here to unlearn the teachings of the church, state, and our educational system. We are here to drink beer. We are here to kill war. We are here to laugh at the odds and live our lives so well that Death will tremble to take us." - Charles Bukowski

He said that and that's why the song is named so. Note that Modest Mouse isn't calling Bukowski an asshole, he's calling God one because of it being a control freak. When he says "I am my own God," I think this bothered Isaac, and he wrote about it.

This is a great interpretation. Isaac Brock is an atheist, so he's probably not approaching this from a religious/spiritual mindset, however.

he may be addressing it with this song

Woa, Bukowski said "I am my own God"? In the next song on MM's album, This Devil's Workday, isaac says "I am my own damn God!". Its interesting how a lot of MM songs are all somehow connected.

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