User feelings when enjoyment is not a priority

Our human factors team are used to dealing with a userbase where their tool choice is mandated and training compulsory. Imagine a military context where the user is pressing a button to fire a cannon on a tank.

They would argue that the 'desirability' of a system plays no role in this context.

Most UX materials I've found are focused of the commercial domain and the desirability is easy to justify but I'm finding it hard given the context.

How would you justify how the emotional state of a user is equally import given the context above?