He's being hostile because you're unironically suggesting something outright paradoxical. Let's play your game and take these things at a perceived "accurate" valuation. If werewolves were real, it shakes up substantial notions established by both fact and physics, including evolution, conservation of energy, parasitic commensalism, metabolism, properties of particular compounds such as silver and their newfound ties to the arcane, lunar cycles, and potentially opens the door to magic's inclusion in the real world, if we attempt to analyze the origin of werewolves. That serves to breed a world so imperceptibly alien to our own that its outcome is outright esoteric. Now, let's see what happens if everyone's given equal rights in Victorian London: a single powerful city's sociopolitics are shaken up to a degree and a white-dominant patriarchy dissolves. Not a state's, not a federation's, not a country's, not a world's. A single city happens to have made some strides of activism. The world, as a collective whole, continues business as normal while London enjoys a post-racial environment. If you were to make the argument that these revelations were made in Victorian London and then explored in a modern era, sure, the world may have some different views on culture and it wouldn't be completely "faithful" to our world. But this is still a chronistically self-contained hypothetical about Victorian London, which is already comparing mountains to molehills in terms of variations. That's why he's getting upset.
I've already said all I need to say, but to conclude, there are some strong insecurities at play for you to realistically suggest a localized establishment of equality would somehow jeopardize or even offend a people