Think of three protons in a line, A-B-C. Proton B is repelled in both directions so experiences no net force.

Now think of 10^50 protons in a line. They're all experiencing net gravity towards the middle.

A is repelled outward, B is not repelled, C is repelled outward.

With gravity, A is attracted inward, B is not attracted, C is attracted inward.

Your idea doesn't generalize. With A-B-C-D-E, only C experiences no net forces along the horizontal axis, while all the others (A, B, D, E) are repelled outward. Therefore the electromagnetic force is not cancelled as you seem to imply.

Of course, in practice, we don't know what the inside of a black hole is like, as quantum gravity is very much unsolved.

Okay, but A and B are both repelled outward and it explodes.

So the conclusion is any proton star would just explode? That's what I already thought.

We like to say gravity is "weak", however it seems to operate on many orders of magnitude larger distances.

Even if you make the argument that the energy complicit in the strong/weak forces is cumutavily much greater than the energy due to gravity, I'm still not sure "weak" is the right word for the job...

Gravity onstensibly runs at infinite speed over infinite area (the effect of gravity waves non-withstanding).