I agree with him though. Not using an equal area projection when trying to compare areas is very misleading.
Using another projection would confuse the issue for non-map nerds. While there are problems with the Mercator Projection, it is what most people are familiar with. For example, showing a projection with Africa sized correctly with the Americas would confuse a lot of people who would think the underlying map was wrong.
The whole comments section is worth a scroll-through: didn't know there were so many map nerds on twitter!