Too much a fan of expanding earth to be a flat earther myself.

Kidding aside: a flat earther will point out that Baumgärtner never got high enough for the curvature to be noticeable, clearly, what we see is the effect of a fisheye lens (otherwise, the picture at 1:14 could be evidence for concave earth). It looks flat enough through the hatch at :47. So this sort of "evidence" looks just as contrived to the "other side" of the fence as the spirit level experiment does to "ours".

Are we making such posts just to mock the others and jerk a circle? That's good for group coherence, "ours" and "theirs". And truly easy.

If we try to debunk them, however, to persuade those still on the fence, or even enlighten those who are lost in the "rabbit hole", I suggest we do so honestly, each claim of evidence after another, even if it requires much greater effort, such as jumping into the labyrinth ourselves, and even if it means danger to our own worldview if we find that not all claims of evidence are as far-fetched as the spirit level experiment, and some may get us scratching our heads.

Personally, I think there are flatearthers who truly believe when they watch and make these YouTube videos, and others perform a very valuable role: that of a Socratic troll. It has become too usual to just lazily accept our received wisdom, instead of questioning it every now and then. And clearly, especially flatearthers have found a vulnerable spot, as the unprecedented amount of pieces on their obvious stupidity and gullibility shows.

If all we can react with is ridicule and arguments that they have already "debunked", we only prove how brittle our world view really is.