I think this song is about being ostracized by people or a community.. the poison people feed you is the apathy or antipathy they express towards you.. and you return those feelings with hatred, guilt and fear... those feelings keep you alive generally because they prevent you from becoming a target of the group. Hatred, guilt and fear can also be used as weapons and to justify dishonourable actions such as cheating, stealing and lying which also allow you to circumvent the wrath of those strong than yourself, whether individually or against a group. The fire of the soul is finally the point at which you aren't willing to take anymore crap and are actually willing to use your weaknesses as weapons.
Just my impression I guess.. and I really love the melody and voice in this song..
Just another couple of thoughts.. being nameless and shameless and being nothing pretty much means you have nothing to lose.. so you can be fearless.. which is obviously a far cry from being courageous, being more similar to being desperate in this context.
I also find it interesting that a good number of merciless and treacherous tyrants in our history come from impoverished conditions or ones of alienation from their original cultures.
