one size does not fit all
consider this:
there is a whole generation of students who are growing up exclusively on apple computers. they have macbooks in college and imacs at home. a few years ago it was strange to consider that you'd come across anyone who had never used a windows PC before, but times have changed.
as an organization, do you really think you can continue to supply your employees with only windows machines?
[EDIT: i know that there are windows-only software packages. however, with tools like virtual box (free from oracle) and vmware, you can easily virtualize a windows environment on the mac OS. stop making excuses.]