In the real world, equal respect for all cultures doesn't translate into a rich mosaic of colorful and proud peoples interacting peacefully while maintaining a delightful diversity of food and craftwork. It translates into closed pockets of oppression, ignorance, and abuse.
Many people genuinely feel pain at the thought of the death of whole cultures. I see this all the time. They ask, "Is there nothing beautiful in these cultures? Is there nothing beautiful in Islam?” There is beautiful architecture, yes, and encouragement of charity, yes, but Islam is built on sexual inequality and on the surrender of individual responsibility and choice. This is not just ugly; it is monstrous.