The obsession with class snobbery exhibited here is by the bitter and twisted ones who ridicule the use of the term on the basis of their own class (inverse) snobbery. Sad how such mindless bigotry prevails among some. It is merely a job title, and conflating it with class is really rather sad.
The term Captain is simply the correct and respectful (aka polite) form of address in this case. Captains do not have to use it themselves and in my experience few do unless, as mentioned earlier, it is useful in smoothing the way in places where gold bars and uniforms smoopth one's passage.
In many places in Europe even the skipper of a small yacht is referred to as Captain by the authorities; customs and immigration officers, coastguard and marina staff. Is that "class struggle" related too ffs?