I think you're being far too harsh on the popular groups of the '60s and '70s - blues and folk music are notorious for stealing from each other, so my only point was to show how ridiculous it is for those same people to cry foul when others do it (albeit more successfully) to them.
And I also think you're being a bit too harsh in general - music (as a whole) seems to really be about adaptation and reinterpretation of what you've heard. More intelligent and knowledgeable musicologists have pointed out clear instances of "borrowings," as we might call them, from Mozart in the works of Beethoven and others. That list goes on, of course, and refutes your point that "others weren't doing it"...actually, it's been done throughout the history of music by just about anyone. Hell, have you ever listened to anything where someone hasn't said "doesn't this sound like...?" Even if it isn't outright thievery, everyone has their influences and it shows...it all gets muddier when you deal with less rigid and more "folk" types of music, because just about everything has been recycled and reused, with attributions to this or that artist. A big part of the anger at your comments, as far as I'm able to see, was that you weren't including everyone else - including the blues and folksmen (and women) - in your cries of "Thief! Thief Baggins!"
The whole "it's okay to copy" thing is itself muddy, though, from some sort of "moral" point-of-view...but it all seems like bull to me, really.
Btw: Peter Green credited "Hellhound on My Trail," a song considered to be a Robert Johnson original (though not without its influences), as "Trad., arr. by P.A. Green" on the Fleetwood Mac debut in 1968.