We do know things about the world. Nothing is absolute in science, but some things come very, very close. Conservation of momentum is one of those.
Yes, it is. And the drive conserves momentum quite fine. Why do you claim it does not, when all the theories about how it works clearly state: it does???
I love this: when somebody complains that the theory of operation is total gibberish, the response is: "But we don't need a theory! Experiment trumps theory!" Then when somebody suggests that one needs much, much stronger evidence before you should even consider tossing out conservation of momentum, one of the most basic principles of physics, the response is "But they have a theory that shows it doesn't violate conservation of momentum".
Rinse and repeat.
I have always been kind of astonished that a group of self-selected tech geeks would repeatedly display such abysmal scientific understanding. Global warming? Not nearly enough evidence for that. Decades of studies and a broad scientific consensus are still not enough to draw an actionable conclusion. But two or three crackpots claim they have a warp drive, and everybody is lining up for their tickets for Alpha Centauri.