Don’t want to be defederated? Don’t let chuds and bigots on your instance. It’s pretty simple.

While this is the main reason for defederation, I think it's important to recognize that humans are going to human and as of such you're going to have defederation over extremely petty issues. In human history we've literally started wars over petty issues, costing countless lives - defederating is small stakes in comparison.

With that being said I agree with other posters that defederation is a tool. Just like any other tool it will be used in ways not everyone expects. A hammer can be used as a can opener if you really want. Or as art. Or in an elaborate machine. Tools may be designed for a purpose, but humans are creative and you can't enforce that tools are only used in certain ways.