[CouncilofTrent]

Ohh so now are you going to argue the meaning of "is", like Clinton?

[olde north church]

Actually, it's not nitpicking, I consider it to be central focus of the "Last Supper". It was Jesus Christ creating the analogy between Himself, the gospels and the Church. The Church is My Body, The Word is My Body, My Blood flows through the Church. It is also a warning not to view the "dogma" piecemeal, consume all of it. No crumb is too small to overlook.
I hardly call that "is" ising, I would have to say you are the one involved in parsing.

[Fatalist]

Psalm 18:2 "The Lord is my rock, and my fortress..."
You do not believe God is a literal rock (or fortress), do you?

John 15:1 I am the true vine...
You do not believe Christ is a literal vine, do you?

But you do believe that a piece of bread is literally the flesh of Christ?

Is there a reason that the first two examples should be taken as metaphors, while the third should not?