The receptivity of the sounds, feelings styles of folk music was created by the environment- many many factors.
People were ready to adopt something that provided those feelings to them.
When all of the above mentioned back country inspired and foreign inspired music turned up it was therefore popular because the qualities it possessed were the qualities that the ears of the next generation looked for.
Many of those who were in possession of the stages and media flavored folk music in a particularly lefty, civil rights way (nothing wrong with those issues) they could do it because they were in power- just like every group in power can set the tone. These folks provided only one channel most of the time to a receptive population.
When the major issues developed they were in command of the ears and went full steam ahead- their concerts no different than any other political rally or propaganda event.
The question is did they lock out the opposing view because of their possession of the media and the stages and power of music?
Anything folk would have been ok for the audiences the essential qualities were there. Seeger did play stuff that was not political however whenever the songs were political they were one flavor.
Of course when the issues came up civil rights, war etc....those fed the single political line naturally followed but more importantly the entire gnere was branded.
yes issues come and go however, folk music has to find a more efficient pathway through them so that it does not have to be frequently be knocked down and revived. The way forward is balance and welcoming of all sides even if you have to work to invite them and bring them all together. If you believe your issues are correct you will not mind sharing the stage and the media.