No argument there. See it all the time.
I've watched some pretty generous and jai dee farang get dragged threw the mud by their "Thai Love"...drained of every dollar they had in their account...and then left discarded (like you previously suggested) like a used paper plate. I've also watched some pretty nasty farang treating the working boys like nothing more than discardable sex objects too. I guess that door swings both ways.
Thais aren't perfect people by a long stretch and when you're submersed in the active sex scene interacting with nothing but working boys the odds of connecting with someone disingenuous are pretty high. I think I heard someone once refer to this as "reality".
I've always believed that answers to these complex dilemmas in life are always somewhere in the "Center". On one side you have farang punters who throw their pocketbooks at the working boys...shower them with expensive gifts...never say no to a request for more money...and take the bait hook-line-and sinker. The term "Walking ATM" was invented for guys like this. Then, on the other end of the spectrum, you have punters who continually abuse the working boys...emotionally, and sometimes physically as well.
I've always felt it best to just treat them the same way I want to be treated...try to use some common sense when it comes to judging their character...draw my line-in-the-sand when it comes to charitable contributions...and take it from there. The middle road. Not an easy touch - and not Darth Vader either.