The simplest version of the argument is:
Things simultaneous to the same thing are equally real.
For any events A and B at different times, an event can be found that they are both simultaneous to.
Therefore, any events A and B at different times are equally real.
As a lifetime lover of Parmenides and Plato, I rejoice in the argument. The Aristotelian-Newtonian attempt to place the standard or intelligible principle for change in the universe failed, and so we are left seeing the universe as a participation in other.
That said, the block universe cannot mean that all events are simultaneous in time. Past, present and future or even earlier and later cannot be simultaneous. This is why the major premise spoke of things simultaneous to the same thing as equally real, though not necessarily as simultaneous to each other. This raises the question of just how temporal divisions can be allowed as equally real but not existing at the same time.
The simplest answer is just to say that the real is broader than the temporal. Without a realm transcending the temporal all times cannot coexist except at the same time, which is a contradiction. In this realm, time is whole, though it exists in its transcendent mode, and the time we know here is necessarily a broken image of this transcendent totality. There is no space-time loaf of the universe somewhere, starting at the big bang, with everything after it worming around. Such a loaf is not only unobserved but contradictory. Better to replace it with something unobserved but at least possible.