Normally a bad employee might fuck up. Then you fire them.

However a bad IT employee can get a computer to automate fuck-ups so more can get fucked up faster. Do you want to find out a week before classes start that the limit on class size wasn't implemented, and everyone thinks that they are registered for all of their first choices? How about having a key-served application install a virus on every computer on campus, at the same time?

Do you still want to risk it?

And then track down productivity studies that document factor of 100 differences in productivity between different developers.

Cheers,
Ben