Evolution implies that animals suffered and died for billions of years
before human beings appeared. This implies that God is not really a God
of mercy and grace, because the suffering was not necessary to create
human beings for fellowship with himself. This, in turn, implies that the
loving God of the Bible does not exist.
Evolution assumes that the conditions of death and suffering in the
past were much like they are now. If death and suffering mean God
was not a god of grace and mercy before humanity, then the same
conditions today mean he still is not such a god.
It is not for us to tell God how to do his job. There is no
justification to claim that from God's point of view, death and
suffering are not the best way to get things done.
Creationism does not solve the problem. It still proposes a god that
allowed 2,000 years or more of suffering and dying before redemption
came. If God is cruel for allowing billions of years of suffering, he
is still cruel for allowing thousands of years of suffering.
Origins are not determined by our personal decisions of what religion
to follow.