“It’s ‘Köln’.”
Not in English. Just as we say Munich and not München. We also say Federal Republic of Germany and not Bundesrepublik Deutschland.
But every time a third world hell hole changes its name, we jump to get on board. Congo - Zaire - Congo. Burma - Myanmar. Rhodesia - Zimbabwe. Ceylon - Sri Lanka. Peking - Beijing. Siam - Thailand. Persia - Iran.
Any time someone brown, yellow or black shouts, we jump. But we can't call our fellow while folks what they want to be called.
Yet we are forced now to say “Bejing” instead of “Peking” and “Mubai” instead of “Bombay”.