I'm thinking of pinning a death metal poster to a church door depicting a disemboweled jesus
Why do you think it's okay to harass and disrupt the church like this?
I want to show my discontent to christianity.
You need to be more respectful of someone's religion. You are basically harassing others and making people very uncomfortable by being so immature like this. You need to have a debate with the Father first and settle your differences, not all Christians are bad people.
I believe that Christianity is a religion of weak people.
You do not have to be a Christian or even like them, but that does not give you the right to be so disrespectful   You would not someone harassing you for your beliefs and should extend that same respect to others.