I understand that salaries are low and that poverty is rife in the Philippines, and have no issue giving money to charity, but like most people here I hate being overcharged with foreigner tax.
Some resorts, bars and facilities actually openly advertise a price for Filipino's and a price for Foreigners. I have been in a bar with a price list with a column for filipino and column for foreigner.

I never lose my temper or get angry, and in the Philippines by doing that you'll just bring yourself more hassle. With taxi's when I have problems, I just tell them to stop unless the meter goes on, and then if they don't, I open the door. It normally works fine, but I have had a guy in Cebu call my bluff, put the meter on and then suddenly say he's got car problems in the middle of no-where and dump me, before dashing off.... In Manila taxi's are a nightmare anyway, most don't want pickups going the wrong direction, can be hellish to even find one at peak hour.