What started the Protestant Reformation was the corruption of the Catholic church and the desire to get back to Scripture, which Catholics claim to have written.
Communion itself is not what non-Catholics reject, it's the teaching that goes against all the Scripture that forbids the consumption of blood.
Eating human flesh is cannibalism and drinking blood is strictly forbidden by God, which is probably why certain groups practice it.
Peter himself said that he had never eaten anything unclean. which would mean that even he did not consider the Last Supper with Jesus to be LITERAL flesh and blood.
Nor could Jesus command people to break the Law and therefore sin.
Or are you going to try to convince us that Jesus commanded people to sin just before He went to the cross?
In John 6 we see those turning away from Jesus because they could not reason the issue in any way other than the carnal mindset, and their pride in following the law overwhelmed their seeing something in the spiritual sense rather than their carnal sense.
In Catholicism we see the adherents to that religion eager to be carnal ( thus be in condemnation) so they can take pride in their 'doing', as if being obedient (while actually being in disgusting opposition to the Command from God which was given long before the Ten Commandments yet was repeated by the earliest council of the Apostles as seen in Acts 15)!
The Catholic's refusal to see the issue in any way but the carnal (eating 'real flesh' and 'real blood' and taking into their mouths 'the soul of and the spirit of' Jesus is proof of the deep-seated pride of self accomplishment), being obedient and thus deserving, gaining merit toward eternal life. The obscenity standing in stark evidence of a works based religion in opposition to the Grace of God in Christ Jesus.
The thrust of Catholic Eucharistic teaching empowers a priesthood, like the Nicolaitans which Jesus proclaimed he hated. It is also satan's way of empowering the religion he splintered off from Christianity, the religion that claims to be the one holy org.