What fallacy is this that's common among Flat Earthers?

I won't necessarily answer but this is a simple ad hominem when attacking the person of what they did instead of the actual argument being that the Modern Artillery Systems use earth curvature calculations.

Though Flat Earth may seem a controversial topic, I think 1. is a loaded question with the cum hoc argument that them using earth curvature calculations means that it has lead to them making accurate decisions based of reality, or whatever the foundation of it is. It would have been better if person 1 had actually proven that it has a significant effect, if it doesn't then it is an insignificant cause and therefore extraneous.