I think one of the roots of that kind of thinking is this myth (which has been echoed on more than one occassion by our "Christian" President Bush):

All religions worship the same God, they just have different names for Him/Her/Whatever).

Nonsense, of course. To this kind of thinking I have two general responses:

First, that the difference between Christianity and all other religions is that while the others say "Follow the rules and you'll be okay," Christianity alone says, "Because we have not and cannot follow the rules, we need a Savior."

Secondly, God has provided one - whose perfect obedience and substitutionary death has secured the salvation of all who come to God through Him. There are not multiple saviors, nor is there any other way than the one God Himself has provided. It simply makes sense that salvation is available only from the One who has purchased it for us. He alone has the right to determine the terms under which He makes it available to us.

-Robin