That is not how the burden of proof works. You have the burden to demonstrate your extraordinary claim of security adequate to stop the NSA, a claim that flies in the face of the overwhelming prevailing trend of insecurity both in the industry and Apple in particular.
Your claim has been made without evidence. It can be dismissed without evidence. And that is ignoring the fact that it is a claim actually made against the evidence, both ambient and particular.
And no, Apple marketing does not qualify as evidence. You need a competent, unbiased, third-party with demonstrated discriminatory power to support such a claim.
I’m afraid you have it backwards. I made only a claim that it hasn’t happened yet, based on the absence of stories that it has. That’s a negative claim, like “there’s no evidence that God exists.” It is not my burden to prove the absence of something. It is the burden of someone who makes a positive assertion (e.g. God exists) to support that claim with evidence.
While you have every right to be skeptical about the security posture of Apple hardware, that doesn’t mean the burden is on me to conclusively prove that it can withstand the possible universe of attacks against it.