It was the snobbishness of the purity rocker scene that inspired the rejects to form grunge. And once grunge took over the mainstream, the purity rockers suddenly found themselves as the outcasts struggling to fit into a standard they didn't make the rules to. And the purity tests were gone.
Not so sure about the 70's-80's rockers -- as you described them -- actually being shoved out as outcasts by the grunge movement.... They grew up, and consequently were no longer that into the whole big hair / leather jacket with studs / boombox everywhere thing. Couldn't wear all that to work, you know.
At the same time, such rockers they still went to some shows. Some 70s/80s 'classic rock' bands like Metallica, Van Halen, AC/DC, Rush, and Iron Maiden were still doing tours throughout the 90s and 00s. Some of the 70's/80's rockers got into the harder hitting grunge bands like Soundgarden. KISW still played AC/DC, Metallica, Van Halen, Iron Maiden, Judas Priest, Rush, etc., along with the more contemporary Tool, Pearl Jam, AIC, etc.
One thing I noticed after grunge hit was that there was no 'purity test', as it were. Anything was fine, clothing wise, hair-wise, and music taste-wise. Things really opened up after 1991-1992. There seemed to be less putting people into a box over whatever music they listened to or preferred.
The first grunge fans I ever met, in the late 80s, dressed like hard core punks. Some of the female grungers dressed similarly to the ones in the Singles movie, though. After grunge music hit the big time, guys' fashion (if you can ever call it that) was all over the map. The stereotypical flannel shirt / worn out jeans was pretty standard clothing in this region for years before it became one of the aspects of grunge fashion.
As for the subject of the OP, some songs always got complaints when heard on rock radio. Even in the 80's you'd see comments on it in publications like the Rocket. Radio always takes the hit for 'not playing the right music'. It's rare when the stars align and music fans seem to rave about a radio station. Usually this seems to be when a music fad hits the big time -- the heavy metal thing in the 80s (KISW, naturally), New Wave (KYYX), Grunge boom in 1992-1998 or so (KNDD anyone?).
The rest of the time there will always be people who will complain, like the construction crew the OP mentions. People are complainers by nature. Radio can't please everybody. No genuinely mass media really can.