She wasn't talking about specific homosexual sexual practices, as in Massachusetts public high schools. She was addressing the evil of homosexuality itself, and its association with other social pathologies.
She was speaking to a high school audience at a Catholic school. It would be no different from speaking about the fate of Sodom and Gomorrah, or about adultery and divorce.
The parents were objecting to the criticism of homosexuality per se.
I know the grounds that those particular parents opposed the presentation. I am saying that me, as a conservative parent, would not want any discussion of homosexuality in any context in the classroom without my permission. This leads to premature sexualization of children not ready for marriage.
Let the confused parents take their kids out and enroll them in the fine public schools who will teach them the “tolerance” they want them taught. Were they just interested in the superior acedemics and favorable school ratings and not interested in a Catholic education. Or running from problems found in public schools, such as bullying, immorality, drugs, shootings, etc.