[user2459]

This question lacks a lot of details, what tech is being used, how experienced the team is, what the build and deploy environments are like, what level of syntax consistency is needed for various reasons etc..

While many programmers are religious about their tool chain there are very legitimate reasons for wanting a standardized dev environment especially with an IDE that does things like syntax homogenization for you. Without more details it's impossible to tell weather this specific individual case would really benefit from the mandate in spite of upsetting the comfort of their devs.