> "You're absolutely allowed to discriminate based on hair color because it's not a protected class."

The "not a protected class" counterargument is self-defeating because it suggests that discrimination was A-OK before that protected class was created by law. If illegality does not imply immorality, as is often said on HN, then conversely legality does not imply morality.

That's the inverse, not the converse, and if we're talking about propositional logic it is not implied by the original statement.

I don't think you're saying anything different than the comment you're replying to. They are themselves replying to the question "well, why not just forbid discrimination on anything except the ability to perform the job", and their answer is the same as your second paragraph.