help needed with some refutations

Our IT Manager is making it very difficult to integrate Macs at one of our regional offices... Quoting his wise words: [i]At the moment I would not feel comfortable with Microsoft entourage connecting into the exchange database. Its been to give problems. No testing has ever been done on this. If something goes wrong due to a mac machine having problems with a windows evironment who fixes it? We have a corporate standard windows pc which we will continue to be used for the forseeable future. It is a higher risk to the business to start mixing environments.[/i] I need your help guys to build up some creative refutations / case studies to fire back. The refutations have to be easy to understand by non-IT people, read management. Cheers, Eric