It was upon this confession, that Christ was the Son of the Living God, that Jesus would build His church upon.
Not a falliable man as in Peter.
You have no concept of “context”.
In first century Greek, petros and petra did not mean “small stone” and “large rock.” As D. A. Carson points out in his commentary on Matthew in the Expositor’s Bible Commentary, the terms did have those meanings in some early Greek poetry, but by the first century, this distinction was gone and the two were synonyms (EBC 8:368).
Furthermore, “the Aramaic kepa, which underlies the Greek, means ‘(massive) rock’” (EBC 8:367), not “small stone.”
Even supposing, contrary to the linguistic evidence, that the two terms should be read as “small stone” and “large rock,” this does not mean Jesus is diminishing Peter in the statement. The anti-Petrine argument assumes that, if there is a difference in the two terms, there must be antithetic parallelism between the statement about Peter and the statement about the rock. I.e., that Jesus is diminishing Peter by contrasting him with the rock: “I tell you Peter, you are a very small stone, but on the great rock of my identity, I will build my Church.”
However, the assumption that the parallelism is antithetic is merely an assumption with no proof. It can just as easily be synthetic, so that the statement about the rock expands on the statement about Peter: “I tell you Peter, you may look like a small stone now, but on the great rock you truly are, I will build my Church.”