Hey Staiduk,Borderstone here. 1st up,welcome!
I can only give my "opinion" of '70s Gordon. I've seen early 70s clips where he seems pretty laid back and friendly too the audience.
In a clip of "Sundown" from a 1974 NBC "Midnight Special",he even encourages the audience to clap along.
I think if he were different in the latter 1/2,it would be to the personal problems I've heard so much about. The divorce,his drinking,WB not being to supportive and eventual low sales of his LP's.
...or,maybe your frieds just saw him on an "off" night.
I saw him in 2002 by the way and he's perfectly "hospitable". :D