I was an evangelical Protestant for 47 years before converting to Catholicism.
If the Protestant does not believe that Jesus is Truly Present, Body, Blood, Soul, and Divinity, in the Blessed Sacrament, then it would be sinful for them to genuflect before the tabernacle or altar. Christians, including Catholics, do not bow down to inanimate objects, as that is idolatry.
Catholics do not bow or genuflect out of politeness just to show respect for the Church. The genuflection has a much deeper meaning than just a polite custom. Catholics bow in worship to the Lord Jesus only. They may bow before a statue of a saint, but only to show respect and to help predispose them to humilty as they ask the saint to pray for them, even as many of us would salute, shake hands, or make some other gesture of respect for a noteworthy person (e.g., the President of the U.S.).
Some Christians do not even bow down to human beings, even if it is a custom of the culture meant to convey respect. Some Christians refuse, and bow to Jesus Only.
I would never encourage a Protestant who does not believe in the True Presence of Jesus in the Blessed Sacrament to genuflect even out of respect for the traditions of Catholic friends. It gives the false impression that the Protestant DOES believe in the True Presence, and this could cause scandal. Another Catholic might observe them and assume that they were Catholic or becoming Catholic, or at least assume that the Protestant believes in the True Presence of the Lord.
Think about it–would you bow and clap before a statue of Buddha if you were with Buddhist friends? Or would you join in a celebration of Wicca with your Wiccan friends? No, I would not. I would sit quietly and respectfully and not disrupt my friends’ worship. But I would not join it.
When I was Protestant, I only began genuflecting (bowing, actually, since my knees don’t work) when I recognized Jesus in the Blessed Sacrament. I did not bow just to be polite. I bowed because He was there, and bowing was the only proper response to the Lord Jesus.
If the Protestant has to “wait” to begin bowing, that will cause them to think more deeply about the Catholic teaching of True Presence of the Lord. We should not encourage people to merely imitate Catholicism, or to adopt Catholic practices and customs that they like. This is what many many of the emergent Protestant churches are doing–picking and choosing Catholic practices that are cool, like lectio divina, candles, contemplative prayer, silence, chant. Rather, we should encourage our friends to study Catholicism and embrace the fullness of the Church’s theology and practices.
