if someone is stupid, and making objectively stupid decisions, it would be fair to call them "developmentally challenged" especially if that person is donald trump, and the stupid decision is tariffs.
Would it also be fair to call him a retard? Yes.
should you? Probably not, would it be justified, yes.
It's only really fucked up if you're using it belittle and demean someone, though there are also situations where this is deserved. Morals and ethics aren't really a solid ground to stand on, more so a floating mass of garbage in the ocean, that just sort of, showed up one day.
fuck mouth might be too insensitive for those of us who have or don't have sex, so basically all of humanity actually.