I came up with the cartoon character "Acoustic Antonio" as the answer to the question: whatever happened to protest singers? It's fitting that a protest singer in 2017 is an imaginary artist since there's a void of such artists on the charts during an era full of constant bad news in the media. In the sixties, back when there were over fifty major news media companies (now there are six), there was more of a sense that media and music reflected what was happening in the streets.
The idea that protest singers come from the streets is a bit distorted, since the biggest examples have come from big labels. Bob Dylan, for example, was introduced to the masses via Columbia Records. If rock and roll was considered anti-establishment music when it became popular in the fifties, it was still ushered in by a big movie company, MGM, which was also the label that released "Rock Around the Clock" by Bill Haley & The Comets. While it can't be considered a political song, it might be considered a fun social commentary song about partying all day and night instead of working. It was certainly an appropriate time capsule theme that captured the spirit of the rising post-war middle class.
The folk movement of the early sixties with Pete Seeger, Kingston Trio, Joan Baez and Peter, Paul & Mary, was inspired by an earlier 40s/50s folk era led by Woody Guthrie, who wrote songs that protested fascism. These acts tended to sing traditional folk songs and mixed in new original songs about the changing times. Guthrie's most famous song, "This Land Is Your Land," was a mix of traditional folk and a modern attitude about cultural sharing. Such sing-along anthems successfully motivated large crowds at folk music festivals. One of the early war protest songs that became prominent in the sixties was "Where Have All The Flowers Gone?" written by Pete Seeger and recorded by the Kingston Trio. It was a familiar peace anthem throughout the decade, although it was never a big commercial hit single on the charts.
Protest songs can actually be credited for helping end the Vietnam War in the sense that they brought people together and opened people's minds about peace. Bob Dylan later downplayed the meaning and intent of his most anti-war songs such as "Blowin' In The Wind" and "Masters of War," but those songs contributed to an awakening in America that wars were not the best solutions, especially for conflicts that were staged by our own government. Defense Secretary Robert McNamara eventually admitted in a film he narrated called The Fog of War that the Vietnam War was based on a non-existent attack known as the Gulf of Tonkin incident.
There were several protest acts in folk and rock in the 60s/70s, but by the disco era of the late 70s the age of the social commentary song was over. The mainstream became flooded with narcissistic dance music about showing off body parts rather than using music as a vehicle for social change. At least we learned from the 60s/70s that music is still useful for unifying groups about causes. The absence of these voices in the 2010s is more a reflection of corporate resistance. In other words, artists are no longer signed for visionary songwriting, it's now about fitting into commercial niches.
But the idea of a singer as a messenger or pied piper of ideology will never completely dissolve. For centuries that was a major purpose of music: to beat the drums of war or ring the chimes of freedom, either for the established order or for revolutionary groups. To pretend music has no power to unify crowds is ridiculous. Music obviously has that power, even if it's just a perception. Music has always had spiritual energy that makes it more important than just a form of commercial entertainment. The protest singer will always have a place in society, even if it's just on the local scene or in documentary films.