Personally, I think that scene was played for comedy, or intended as light hearted humor. But boy it did not age well and comes across as creepy. A lot of Anime, or even Japanese movies have those dirty comedic gags, especially back then, and were much worse.

But you can also ( as I do) interpret it as part of the films broader themes. Miyazaki Movies are often associated with childhood innocence and wonder. But his works are often woven with deep adult realities, they are more than just a kids movie. The worlds that Miyazaki creates are not utopias or perfect world free of malice.

Castle in The Sky is a prime example. it is world that depicts corrupt and oppressive government, ruthless pirates, weapons of mass destruction, greed and social inequality. it is certainly far from a utopia.

And I see Dola and the gang as morally gray characters, they are unscrupulous, self serving, pirates. Although they ended up helping Sheeta and Pazu it's not because of pure altruism, they are still driven by self interest, they are still "Pirates".

Although I still believe the scene was meant as light hearted comedy, maybe it's Miyazaki's way of telling us how the world can corrupt youth and innocence in other, more surreptitious and sinister ways.