I've read 12 of Vonnegut's books. He is fundamentally a social progressive, but there are also some moments in some 70s novels (particularly Breakfast of Champions) that I find homophobic. He also has a habit of making women either passive pleasers or full nutso.

But he also explicitly and repeatedly pushes kindness, egalitarian social justice, and willingness to change.

I highly highly recommend every human read Mother Night.