Catholics believe in the Real Presence of Jesus Christ in the Eucharist. Kneeling has always been considered a sign of reverence. Up until Second Vatican Council II (1965), communion was distributed on the tongue to those kneeling at the communion rail. That rule was modified to allow the distribution of communion in the hand to standing communicants.
Recently, the USCCB (US Catholic Conference of Bishops) announced:
"The U.S. bishops' Committee on the Liturgy has said that Catholics should not ordinarily receive Communion while kneeling."
It is nothing but the opinion of a small group of bishops -- a committee. Tremendous grief and problems have arisen in the last 30 years because of the "authority" unjustifiably accorded (by individual bishops, priests, and laymen) to statements of mere committees -- particularly this notorious Liturgy Committee (and its 1970s document on art and architecture, for example). A committee has NO power whatsoever, except to propose its opinion to the entire bishops' conference. This was later clarified to state that NO catholic can be refused communion if they choose to kneel.
Obviously, Fr Irace was wrong to refuse communion to Mr. Black.
Phil 2:10 - that at the name of Jesus every knee should bow, in heaven and on earth and under the earth
If at the very name of Jesus "every knee should bow", then kneeling before Him makes perfect sense (at least for the @30% of Catholics who still believe Our Lord is present, Body, Blood, Soul and Divinity in the Most Holy Eucharist).