sympathy

i m alrite with person who is rude to ppl around him/her, it is forgivable, s maybe tat his/her nature to b like tat. But i m not ok with ppl who is so polite/gentle with a certain majority of ppl bt d next moment b rude a fraction minority ppl. Since he/she can b trained to b polite, y cant he/she be polite to all? Is it more easy for tat person? I sympathy tat person sometimes, have to wear a lot of masks