I don't believe you are being overly sensitive Bill, I get it all the time.
For example, some people engage me, paid the fee without question, use me like a hired gun and then discard me matter of factly when they have no further use of me. That's the nature of what I do, it simply goes with the territory. I expect nothing except maybe some work in the future or referral.
However, with regards to voluntarily helping people out of the kindness of your heart, it can be very disheartening.
For example, I am a member of PC&D's Ask the Expert's panel. I can count on one hand the number of times that people have taken the time or common courteousy to thank me for helping them either solve their issue(s) or point them in the right direction.
Again, I believe it is just a sign of the times; dog eat dog, take no prisoners at any cost, all I want is more than my unfair share.
With the proliferation of free stuff on the www, I believe that many people have lost sight of value. Why should I paid for it when I can find it on the web for free. Of course, what you find free on the www is often watered-down or too generic to have much practical value. But its free. If its free, why should I thank you for it? I can get free anywhere.
I wouldn't get too discouraged. You are a good man and this website and your voluntary efforts to truly help people underscores this.