Muslim reformists, liberals, progressives who oppose gender separation are often very aggressive and their aggressiveness matches the indignation they feel at the notion that genders should be separated. But why is this such a problem? Even the most secular societies impose gender separation to some extent. Bathrooms are gendered. Locker rooms are gendered. Sports are gendered in general. Secular societies recognize male and female and operationalize those gender distinctions in countless ways.
Muslims simply operationalize gender somewhat differently. But since Muslim practices and gender separation differ from the dominant, Western model, that is a problem. Rather than just acknowledge that Muslims do it differently and that, from a truly secular perspective, there is no reason why the Muslim way is worse than the Western way, these reformists and critics of Islam make it seem like Islam is the only religion and worldview that facilitates gender separation and is therefore backwards and barbaric.