Why do they kill John Coffey in King's The Green Mile?

John Coffey is seen as a threat.  From the outsider's
point of view, Coffey is responsible for the death of two little girls.  A combination
of factors are manipulated to paint a picture of Coffey's guilt.  The fact that he was
found with the girls' bodies, their blood on his clothes, him weeping at the site are
all elements that are used by the prosecution to prove his guilt.  At the same time,
Coffey's gargantuan size and his ethnicity are subterranean factors in his prosecution,
with the belief that a man of his size and man of color would prove threatening to the
White establishment.  Coffey's death becomes a stinging rebuke on the chance for
humanity to find redemption, as Coffey is not a killer.  His ability to breath life into
human beings is what compelled him to find the two girls and try to save them. The blood
on his clothing was due to him holding the girls near him in trying to breath life back
into them.  His weeping was not about him being caught, but rather his failure to save
their lives.  Holding the girls becomes a stunningly powerful moment where the need to
give life after it has been unnaturally taken away is completely denied.  Yet, not
understanding all of these elements, the prosecution issues him the death sentence.  The
implication of this is that the killing of Coffey, the redemptive power of life that can
provide hope and salvation, is a reminder that the human race somehow takes sadistic
pleasure in taking life.