The purpose of the primaries is to weed out the contenders until we arrive at a clear-cut winner.
If Giuliani became the nominee, the conservative wing of the Republican Party would, in effect, be marginalized. After all, if the RNC knows they can nominate someone as far to the Left (compared to other candidates) as Giuliani, why should they bother courting conservatives in the future?
IMO, that is exactly the purpose. Marginalizing all other candidates at the Rudy alter is what his supporters are all about.