People seem to parrot that diversity is their strength, but I've never seen a compelling proof that it is so, and all research seem to prove otherwise.

Yes there are societies which are tolerant and diverse, but societies which have the same amount of freedoms with lower amount of diversity will perform even better. I'm mostly talking about cultural & religious, but economical diversity as well.

Yes, countries run into trouble when people start voting tribally, not on the issues. Diversity has some benefits, but it also has downsides. I'm suspicious of people who deny either.