> > But the verb "to be" is still special. Otherwise people wouldn't ask "who are you?" but "who do you be?". It's strange how it can be special in one sort of sentence and not special in another.
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> This isn't responsible for the "be not" argument, but it may describe the apparent unusualities over "to be." Our verb "to be" serves two distinct functions. It is the verb to exist, and also the copula (linguistic equals sign).

To say basically the same thing as Matthew said from another perspective, "to be" what's called a linking verb, as opposed to an active verb, which means that sentences that use it are transitive ("He is the manager" = "The manager is him"), which certainly fits the properties of a mathematical equals sign.

Objects of linking verbs aren't technically objects at all: the subjective case is used on nouns on both sides of the linking verb. So you'd say "I am he," rather than "I am him," while you'd say "I ate him," rather than "I ate he."

The bottom line is that while there are a lot of weird special cases in English, this isn't one of them.