It was no secret that Kurt Vonnegut was a humanist. The man was the honorary president of the American Humanist Association, so that's kind of a dead give away. But what is humanism? A quick answer would be "any outlook or way of life centered on human need and interest" (Source). So it's no surprise that Cat's Cradle is just brimming with humanist philosophy. The novel attempts to get its readers to see beyond political, national, economical, and social borders. It just wants you to view human beings for what they are: flawed, beautiful, and crazy creatures who are more like you than you'd probably (definitely) like to admit.
In connection with Bokononism, Cat's Cradle may be arguing that humanism is complete and total foma. Of course, that doesn't mean it isn't of value to humanity all the same.
Angela's maternal instincts actually prevent her from acting as a true humanist would.