Team member is vehemently against code formatting
I am the manager of a small team of developers (5 engineers, including me). A few months ago, on the suggestion of another colleague we introduced mandatory code formatting in the code base, for our main project. Our project is in Python and the formatting tool is black (not relevant, I guess). I find value in having the same 'appearance' of the code in all the project files, for me it is part of the Quality Assurance for the whole project. Code merge requests have to be formatted with the tool otherwise they cannot be added to the software. Since then, a colleague is always complaining and expressing disagreement about this decision whenever the occasion happens. How would you deal with such situation ? What would you answer to "code formatting is totally bullshit", "it's like colors, some people like it red some other blue that's it", "it reduces my freedom", "it makes code more complicated to read with no added value" etc. ?

I am the manager of a small team of developers (5 engineers, including me).
A few months ago, on the suggestion of another colleague we introduced
mandatory code formatting in the code base, for our main project. Our
project is in Python and the formatting tool is black
(not relevant, I guess).
I find value in having the same 'appearance' of the code in all the project files, for me it is part of the Quality Assurance for the whole project. Code merge requests have to be formatted with the tool otherwise they cannot be added to the software.
Since then, a colleague is always complaining and expressing disagreement about this decision whenever the occasion happens.
How would you deal with such situation ?
What would you answer to "code formatting is totally bullshit", "it's like colors, some people like it red some other blue that's it", "it reduces my freedom", "it makes code more complicated to read with no added value" etc. ?