The evil of the Canaanites has been discussed elsewhere, how they grew so wicked and cold they eventually slaughtered even their own children by sacrificing them to idols - though of course doing so to anyone is evil.
They likely
didn't start this way, of course. Romans 1:17-32 provides a good summary of how
a nation starts a slippery slope by doing evil and not following God's plan to
show grace and mercy to everyone. Yes, sin must be stopped, but since we are
all sinners it must be done with love towards a person involved so they can be
taught God's love. Otherwise, eventually it becomes so filled with evil that
there is no longer any knowledge of what good and evil really are. And, the
human heart is filled with wickedness because of the lust of the flesh, the
west of the eyes, and the pride of life, so people naturally gravitate toward
the evil when there is no knowledge of God and his saving grace. Because, it is
that saving grace that causes us to become new creatures when we are in Christ.
By the time
Abraham receives God's covenant to him, though, they were clearly pretty far
down the road to that extreme evil, though. God promises to give Abraham that
land, and when Abraham needs to find a wife for Isaac, God tells him to have
his servant go way back to his homeland instead of having a wife from among the
natives. He wanted to make sure those people were not polluted with evil. Of
course, there were Gentiles who ended up marrying into the kingdom and even
into the genealogy of Jesus. However, these were people who clearly had
repented of all that evil.
God can do
anything with a willing and repentant heart. That is what he wants of all of
us, He is not looking for us to be perfect before we come to him. He wants us to
come to Him so He can perfect us. Of course, we need to do our part by allowing
Him to, but His grace and mercy is sufficient to keep us saved.
The Canaanites,
however continued to go further and further away from God. Indeed, with Goliath
and other giants in among the Philistines, it's possible that the Nephilim also
being there after the flood means that the angels who left their first estate
may have been involved, if that is the meaning used in Genesis 6, as mentioned
earlier. The evil of sacrificing children show that they were in some ways
totally lacking natural affection. This is one of the signs of the end times,
that many people would lack natural affection, along with being lovers of
themselves more than others and many other things. We can see in how God showed
patience with them, however, before allowing them to be conquered and destroyed
that God's mercy is incredible. It will, however, eventually run out for those
who have not received His free gift of salvation.