1 Cor 10:16 The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ?
17For we being many are one bread, and one body: for we are all partakers of that one bread.
And when one partakes of "that one bread", one is admonished to discern it properly, with all that attends that idea. And certainly there is a disagreement how "that bread" is discerned in Communion.
Agreed. And as Communion is a public confession that one's beliefs are in consonance with their brethren at the rail, a guy needs to be careful about his actions lest they are misconstrued and cause one of weaker faith to stumble.