If you are literally offended by somebody wearing sensible clothes to the point where you would call them "rude" on that basis alone, I would posit that we're a

If you are literally offended by somebody wearing sensible clothes to the point where you would call them "rude" on that basis alone, I would posit that we're actually discussing your mental state, not anything wrong with their clothing per se. Yes, you might wear a suit when you want to kiss up to someone. But being gravely offended by somebody not actively kissing up to you is much less becoming of a mature adult than the act of not wearing a suit. The clothes do not hurt you, they do not deprive you of anything — the only problem is that they don't flatter you. But expecting flattery is uncouth, even if you are accustomed to being flattered.