Team Member Conflict

Are you a developer yourself? Are you able to do the team member's work yourself? If not then you should never ask a developer such a thing. Non-technical people should never get into the details of the work performed by the project team members.

I don't know what your exact situation is but developers often change the low level tasks that they have to do while they complete a requirement. For instance the developer thinks at the beginning to do the work in a way but while working he figures out that his initial idea is not good so he needs to rethink it.

Probably many developers would freakout if they are asked to breakdown their work in very small low level tasks.

I don't want to offend you and I may even be wrong but this sounds like the scenario in which the non-technical PM does not understand the work in details and asks for things that he thinks would be helpful but in reality such requests just make the life harder for the team member.

Senior developers usually ask entry level developers to breakdown the task in very small low level tasks but this is usually just for learning. Otherwise is extreme micromanagement even when the one that makes the request is very technical.

Freaking out is the aggressive reaction when feeling attacked (he could also just have run away or silently nodding without a visible reaction). In the end, your applied servant leadership technique put pressure on him.

There can be many reasons why he felt attacked, status/gender difference, not feeling respected (because he already rejected and you come back), uncertainty how to break the task further down, feeling you are taking away his freedom how to work (and you said you want to have more control), and perceived unfairness (being the only one being asked).

Suggest you find that out. Changing his behavior to do anthing, you can try Grenny's 6 fields of influence:
1-2 motivate him to do it AND enable him how to do it.
3-4 Get buy-in by the team to agree on doing it (building group pressure) AND giving the team the means to do it (e.g. creating a team charter).
5-6 Lastly, establish an environment for doing the thing you want (e.g. publish deadline shifts, customer feedback, .) AND find means to enable this environment.

Hope this helps. Let me know if you want more specific help.