The point is man can thrive without carbohydrates in their diet because both fats and proteins can be metabolized into sugars for energy (ketogenesis).

Man can't thrive on emergency process.

It's like driving a car when ECU detected a sensors malfunction but still allow you to move somehow using emergency fallback tables and workaround mode.

Stop this bullshit. Humans like sweet taste for a reason. It is nature itself helps humans to find most efficient food.

You can't live, let alone thrive without fats and proteins though.

You can't live without salt too, that does not mean you should replace everything with salt.

Sugar is in no way a reason for obesity, diabetes or whatever shit they attribute to sugar. It is just a consequence of body wrong doing, so it can't properly use and utilise sugar. If your brain don't consume glucose as intended, then this glucose will go somewhere else. But it is not a sugar fault. It is your fault that you prefer to grow ass instead of making your brain work.