I can agree with some of what you wrote, but not all. We have become friends with our barber and I always overtip him. I'm also happy to give the gas station dudes and moto taxis an extra 50 or 100 pesos, depending on what they did and what's in my pocket. Same with the bagger boy. I would normally give them 30 pesos but if I don't have change, 50 is not a big deal.I recall there was a thread about this a while ago, where basically some were bragging on how much do they pay for this and that or tip, as the "going rates" were not appropriate for them as that would be been disrespectful towards the workers. The problem is exactly the above, in my opinion. The market is what it is, one person, foreigner or not, cannot change it. If the going rate for a taxi ride is 150 pesos and you decide to "tip" 500 pesos, that does not exactly give a good impression of you and then the driver will be expecting that the same time as well...
I would say that only those people call others "tacano" who have no idea of working...
But no, I would never tip 500 for a 150 moto ride. That's just silly. I do tend to be more generous with people I know.