No offence mate !!!
I always remember when I first spoke to a filipina friend, she called me sir , to my surprise! But of course "po" is commonly used as a mark of respect, just like "kuya", "ate", or any title like "doc" . I guess it's a sign of the times here that if someone calls you sir in the UK you wonder if they're taking the p*ss (same if someone calls me doc in the pub!)