You cannot properly judge a word by its origin. Eg "circular" is not a characteristic commonly attributed to desks (from greek "diskos"). The german word "Mohr" is essentially outdated and out of use, which might indeed give it a strange feeling. However the very fact that the petition's authors seem to feel the need to use etymology might be seen as an indication that even to them the word by itself does not actually feel that offensive.
kilde: