How Do We Know We're Not Brains in a Vat?

In the comments here a Christian said, "you cannot use the scientific method to show you are most likely not a brain in a vat WITHOUT begging the question." Luiz Fernando Zadra responded nicely as follows:
You can use Occam's Razor to eliminate the Brain in a VAT theory, since it has two layers of complexity: simulated and actual reality instead of just one actual reality. Simplicity is one of the core principles of science. Between 2 equivalent models, we know that the more simple is most likely to be true.

All evidence we have points to the fact that there are other minds, that we are brains encapsulated into bodies that can walk around. No evidence at our disposal gives us any clue that we might be a brain in a vat. Such evidence could be produced by the scientist who keeps you in the vat. But unless the scientist show himself to you, maybe exhibiting "god like powers", the belief that you are a brain in a vat is not granted, so we can simply discard it.

This may sound thin to you, but if you analyze the scientific enterprise closer, you will see that every scientific conclusion is achieved in a similar fashion. Nobody will ever prove that gravity will keep working, and indeed, you are irrational if you believe you will start to float someday.

Your brain in a vat theory is a useless model of reality. It does not produce any verifiable predictions and has no corroboratory evidence. In other words: bullshit. As far as I know, it is better to believe less bullshit than more. And that's precisely the scientific enterprise. Eliminate the bullshit in the hope that what remains is the truth. And that's it. Take it or leave it.

The further discussion went like this:

"But the problem is that your are assuming that Occam's Razor is ALWAYS valid."

Zadra again:
Occam's Razor does not claim 100% certainty. If you want certainty, go to the church ask for a revelation. If you want to know how reality is, then you should consider the following:

When facing equivalent theories, the one that is more simple is most likely to be the right one. Occam's Razor does not claim that this will always occur, it says it will most likely occur. This claim is not circular. It is supported by empirical evidence, statistics and ultimately, by the rules of logic.

"I am a simulation of some UNKNOWN aliens who simulate EXACTLY the world I see around me."

This theory is more complex then the objective world theory, since you will have to explain the simulated reality and the aliens reality. Occam's Razor alone is enough to dismiss this claim as most likely false, because we have an alternative theory that is more simple - the objective world theory. If you have evidence that more complex theories are preferable to more simple theories, feel free to provide.

But this is not enough. The extra stuff in your theory (the aliens and the simulation) does not help you to explain anything in the world. It does not give you any additional predictive power. You have no corroboratory evidence for it. The claim that we are not in a simulations is falsifiable, while the claim we are in a simulation is not. And we know that things that are non falsifiable, with no predictive or explanatory power and no corroboratory evidence are most likely bullshit. Again, this is not the case always, but it is the case MOST OF THE TIME.

If you have evidence that this method does not work MOST OF THE TIME, or if you have a better method to separate facts from fantasy, please provide. If you do not trust this method, then please stop using your computer. We know it is reliable using exactly the same epistemic tools I gave to you right now.