[metmom]

This measure was also necessary as a deterrent. One who pardons enemies and does not avenge them in kind, emboldens those enemies to fight against them.

Excellent point.

Those engaged in such evil see mercy as weakness and it emboldens them. They do not understand mercy.

[silent majority rising]

I think that is why God made it a commandment (mitzvah). He also commanded that they defend themselves...Not a Christian commandment as it is taught in churches (turn the other cheek etc.)