Archbishop Chaput said there will be more than 70 speakers, and all of them will be faithfully presenting the Catholic Cburch's message. In other words:
No speakers for gay marriage, gay fornication, straight fornication, contraception, divorce/remarriage without annulment, polygamy, etc.
But sinners? Sure sinners can come. If you excluded sinners, the attendance would be very small.
But nobody's allowed to promote or advocate for their particular fave sin.