Actually, it's quite genius.
Like weeding an unattended garden.
99.9 % of the people reading it will scoff and delete it. The garden has become self weeding.
The only thing left is the 00.1% who will actually reply.
They didn't have to spend time or effort trying to convince anybody of anything. They instantly found the target audience and got everyone else to leave them alone.
If the other 99.9% would write him back, each and every time, his mail account would implode and put him out of business.