I disagree, Sin was created purely for Yu Yevon's protection while he strived to continue his peoples way of life. I don't think it is known the exact purpose of Sin, other than to protect YY, so the genocidal nature of Sin have been an unfortunate after-effect. Akin to the Hiroshima bomb perhaps?

Sufficed to say, unless Zanakand was threatened with total annihilation within what remained of YY's life, it is very unlikely that Sin would ever have been created.