There's some interesting psychological issues in this thread for example the mis-guided notion that - If I address you as Sir I am signalling that I am inferior to you. The real problem here is one of perception of ones demeanor and status, the lower the self esteem the greater the need to shore it up with objections to correct forms of address.
What's the problem with polite address? It doesn't bother the Americans who will even refer to their fathers as Sir.
Get a life be polite address a Captain as Sir or Captain and earn yourself reciprocal respect.
For more information on correct forms of address consult:
1) the Home Office
http://www.ind.homeoffice.gov.uk/ind...%20ADDRESS.pdf
2) Debretts