When I started publishing my blog I quickly learned that explaining why people are wrong is a waste of time. One reason is because arguing with people on the Internet is futile. Another reason is because positive claims are more general than negative claims. I recently realized the problem goes even deeper. Explaining why someone is wrong is even less general than making a negative claim.
Suppose a Flat Earther makes the claim "We know the Earth is flat because an airplane flight from Mexico to China goes over the Bering Sea. If the Earth was spherical then the flight plan would follow a line of longitude instead." Obviously, the Flat Earther is wrong. The reason for the (seemingly) curved flight path is because the shortest distance between two points on a globe is a great circle. Great circles do not equal lines of longitude (except for the equator).
My argument about great circles is true but it is not very useful. Falsifying the Flat Earther's argument does not prove the Earth is round. It doesn't even prove the Earth is flat. All I proved is that this particular argument fails to prove that the Earth is flat.
It is easier to generate bullshit than to refute it. Refuting bullshit is a whack-a-mole war of attrition where the bullshitter has the advantage. The best way to deal with bullshit is usually to ignore it. Fighting bullshit in general is as futile as trying to cure stupidity. Individual bullshitters, on the other hand, can be dealt with.
The best way to deal with an individual bullshitter is to tell the truth and explain how you, personally, arrived at the conclusion. "I know the Earth is spherical because…." Keep yourself clean by occupying the intellectual high ground.
But, sometimes, when you really want to destroy someone, you can ask him/her to place bets. You think it's daytime on the other side of the planet? I have a friend there. He has a camera. How much are you willing to bet that he can't see the stars?