"Besides, globalisation will overall increase the total wealth of the poor + middleclass combined."

It won't really increase the overall wealth of the middle class. It will pull wealth away from the middle class to pay the poor at a cheaper rate. This is what's happening right now and why people in the tech industry are so upset by it. It's a form of global wealth redistribution.

I also don't think the middle class has any divine right. They just need to start preparing for job loss and overseas competition.

Trade has ability to create wealth. If we increase global trade, it will also increase the total wealth available to the poor + middle class. Some portion of the surplus value will also go to rich providing the capital.