being a white guy in ancient egypt, any pre colonization of african country, any middle eastern country.
a large part of frances history being an english guy isnt exactly favored upon.
and they could always just, ham it up a little bit like legends of tomorrow does. outside of obvious conflicting periods like the american revolution fire storm being black is largely handwaved unless theyre forced to bring it up.
the doctor is already hated/wanted by a large portion of the galaxy if the doctor can outrun daleks and cybermen im sure he can outrun slave owners with sticks and muskets