I get the source of your anger.
Riddle me this though, if the writers of said stolen songs had such gold why were Jimmy and Co. able to cash it in?
My point being why did LZ have success w/ the "stolen" songs and the original artists did not?
Could it have anything to do with the way the songs were rearranged by Jimmy Page and oh wait I am pretty sure John Paul Jones( a phenomenal musician and songwriter himself) may have had some input also.
Could it have anything to do with the extraordinary talent found in LZ ?
No couldn\'t be. 
As much as I LOVE Led Zeppelin I have to agree with Cobb.
LZ cashed in like many of the bands of that age by playing "black" music to white audiences. Most of the British Invasion was exactly that. White kids playing black music was much more acceptable and was played on stations that would normally not play that kind of music. lets not forget that Zeppelin started in 1968. Sure a little later than the initial invasion but many white kids were not versed in traditional black music and Blues.
So it seems that when confronted with a lawsuit they settled out of court and made good. Should they have done it from the start probably but the black musicians were basically victims of the times and many of them stole the music from others and traditional hymns and work songs etc.