The reason might seem odd. But it ocurred to me that if you want to use immigration to reduce crime, including rape, the obvious solution is to ban all male immigration.

That shocked me because it seems so wildly discriminatory. Yes, most violent crimes are committed by men. But very few men commit violent crimes. Banning male immigration would punish a large group for the appalling actions of a few. Making it about "$some_country's men" doesn't seem a whole lot better. It's still unjust to punish someone for someone else's crime.

If anyone is curious about the exercise, I recommend trying it. It was disconcerting to sit with the idea of banning male immigration, really seriously consider it and realise how viscerally shocked I was by the idea.

Edit: for context, in the UK right now, phrases like "rape gangs" are part of the debate/argument about immigration.