Disclaimer: I also am not in sailing circles and also have not seen the documentary in question - I'm basing this impression entirely on the hearsay of an extensive Reddit thread (that I cannot alas find again) full of sailors who had no idea about Moxie's other life. The objections I remember were:
-incompetent sailing
-criminal behaviour (or more likely faked criminal behaviour) including theft
-making a big show about being poor and bohemian when in fact they had loads of cash (some of which was spent on the boat offscreen, rather subverting the message)
This is exactly the same kind of pseudo-rebellious sketchiness as pretending to ride your motorcycle illegally through Chernobyl, when in fact you took the official tour.
(I have just queried a sailing IRC channel and got a similar response, so I don't think I'm misremembering.)