How does the situation arise? I mean, 15th century England regarded anything outside its immediate boundaries as irredeemably alien (in fact, this parochialism extended into the 18th and 19th centuries; the people of Hartlepool are still known as the "ones who hung the monkey" when a pet ape escaped from a merchant ship and was hung on suspicion of being a French spy) but, on the other hand, there's a very small non-white population and that predominantly in seaports.
Personally, I detest historical fiction where the MCs are saddled with a whole slew of anachronistic attitudes to sex, race, class and sexuality because the author's worried about being thought to endorse attitudes simply by depicting them, but, on the other hand, there isn't any need to go too far the other way when it's so far back; for example, a lot of the cruder racial/eugenic theory only emerged in the 19th century, and was a hardening of attitudes on the back of colonialism from earlier tolerance.
Mind you, casual cruelty and outright religious bigotry were rampant; your hero might be relatively tolerant to a Moor as a man, but loathe the very thought of islam.