At a certain point, Long John Silver uses his parrot, Captain Flint, to teach Jim a moral lesson. He points out that Captain Flint swears a blue streak even though she has no idea what she's saying. In other words, she's been around bad company for so long that she can't help behaving badly herself. It's just the way of nature that, if you mix with bad company you become a bad person (claims Long John Silver, and we guess he would know).
This is why we think it's significant that Abraham Gray, the one loyal sailor in the whole crew, is on his first sea voyage, fresh from the countryside. He decides to ditch Israel Hands and join Captain Smollett during their first skirmish aboard the Hispaniola because he hasn't spent enough time around his fellow crewmen – pirates all – to be corrupted.
Sadly we can compare his experience to the equally youthful but more easily persuaded Dick Johnson, who is too weak-willed to stand up against Long John Silver. Dick Johnson winds up abandoned on the island and sick with fever while Abraham Gray gets a share of the treasure and a ride back to England for his troubles. These different fates seem like a pretty clear lesson that it's a good idea to stick to your principles and stay loyal to your bosses – you may get a hunk of treasure out of it.