I first heard Pete Seeger singing "Goodnight Irene" with the Weavers when I was a boy of ten, just before he was blacklisted. I first heard him live about a decade later when my first wife, a folksinger and guitarist and poet, among other things, took me to hear him.
I was a jazz musician and had some attitudes about the folkies that got dispelled that evening. When Pete got the audience to sing along, I resisted at first, too cool I thought, but by the end of the evening I was singing louder than those around me, and possibly more enthusiastically.
Pete Seeger was a force of nature, whose example I wish I could live up to as an activist, creator, father, husband and friend. I didn't know him personally, but from what he showed in his public life and what those who knew him have said about him over the years, he was the real deal.
Here's a clip I found, a trailer for the documentary about him, that sums him up better than others on Youtube: