It’s not just non-Catholics. A large number of people who consider themselves Catholics don’t believe in the real presence either.
Granted, but a Catholic who does not believe in the real presence suffers more from a lack of faith than a genuine theological disagreement.
St. Ignatius wrote in his letter to the Romans:
“I have no taste for corruptible food nor for the pleasures of this life. I desire the bread of God, which is the flesh of Jesus Christ, who was the seed of David; and for drink I desire his blood, which is love incorruptible.”
He also wrote to the Smyrnaeans: (emphasis added)
“Take note of those who hold heterodox opinions on the grace of Jesus Christ which has come to us, and see how contrary their opinions are to the mind of God . . .
They abstain from the Eucharist and from prayer because they do not confess that the Eucharist is the flesh of our Savior, Jesus Christ, flesh which suffered for our sins and which the Father, in his goodness, raised up again. They who deny the gift of God are perishing in their own disputes.”
Irenaeus:
He has declared the cup, a part of creation, to be his own blood) from which he causes our blood to flow; and the bread, a part of creation, he has established as his own body, from which he gives increase unto our bodies. When, therefore, the mixed cup [wine and water] and the baked bread receive the Word of God and become the Eucharist, the body of Christ, and from these the substance of our flesh is increased and supported) how can they say that the flesh is not capable of receiving the gift of God, which is eternal life — flesh which is nourished by the body and blood of the Lord and is in fact a member of him? (Against Heresies 5:2 [A.D. 189]).
These are two early Christians who are clearly on board with the real presence. More importantly, there is not a point where there was a teaching against the real presence, only to have that teaching be replaced by the current dogma.