I have no problem with Barbra Streisand voicing her politcal views at a concert, especially with Hillary and Bill Clinton there.
It happened often during the war in Vietnam and earlier during the civil rights struggle. Joan Baez and Jackie Washington sang about civil rights in Cambridge, Northeast U and Sympathy Hall. Bob Dylan sang his protest song of the 1960s, updated to include Nixon. I never saw Frank Sinatra, but knew he was friendly with Reagan and Nixon's former vice president, Spiro Agnew.
Janis Joplin, Tony Bennett, Ella Fitzgerald, Sarah Vaughn, Cleo Laine seldom talked about politics U2, Patti Smith, Jefferson Airplane, Bruce Springsteen, Pearl Jam are far more politcal. Keanu Reeves and his band Dogstar were silent about everything!