Deacons are not laymen; they are ordained clerics. Diaconate is the first of the three major orders: diaconate, priesthood, episcopate. Deacons usually receive three years of preparation in scripture, moral theology, patristics, Church history, canon law.
Homilies are to be based on the scripture readings of the day. I preach every three weeks, and I spend a solid ten-fifteen hours preparing a ten minute homily.
needless to say, the abomination of a rock and roll Mass in Rochester, where a mass attendee named Judy was called upon to opine about something or other for the homily, is beyond offensive.