Your pretend protestant says “Jesus never told you to turn the bread into His Body during your celebration”. Maybe you should ask him "Then HOW ON EARTH do YOU explain how Jesus made it possible for men to carry out His command: 'Except you eat the flesh of the Son of man, and drink his blood, you shall not have life in you.’? "
Maybe he’ll say, “Jesus was just speaking figuratively (or metaphorically or spiritually)”. Then ask Him “who do you think YOU are to make such a judgement as that - when Christ’s word’s HERE are completely EXPLICIT”
Protestants seem to assume that EVERYTHING that Jesus wanted us to do or believe was written in the Bible. But Jesus did (and said!) many other things - as St. John says (see quote below)! He most certainly could have said other things at the Last Supper. And His Apostles would have UNDERSTOOD what He MEANT when He said “do this in memory of Me”. His Apostles not only understood His words as “intelligent men”; He enlightened their minds to see far more than we do when we read the Gospel.
*John 25 But there are also many other things which Jesus did; which, if they were written every one, the world itself, I think, would not be able to contain the books that should be written. *