What's more frustrating about claims like this are the premises that suggest IPSEC is somehow unknowable. IPSEC is far better studied than OpenVPN is, and its underlying protocol is simpler than TLS (which, of course, NSA is also routinely accused of having tampered with). More importantly: these are protocols, not ciphers. Not only can we read and simulate and test them, we can in fact prove things about them computationally.
I don't know how to articulate the succinct and conclusive argument that you're "not even wrong", but that's the territory that claim lands you in.
This isn't a coherent theory of NSA interference with IPSEC, but rather a collection of different theories, many of which pertain both to IPSEC and (via TLS) to OpenVPN.
* Here's a deep dive on that OpenBSD IPSEC backdoor theory (long story short: it wasn't one, though even if it had been, it would have affected only an old version of IPSEC): https://news.ycombinator.com/item?id=2014197
* Virtually everyone I know in cryptography believes BULLRUN to be a code name for Dual EC DRBG, which is a backdoor, and targets TLS.
* The Diffie-Hellman attack referred to here was discovered first in (you guessed it) TLS.
As for zero-day attacks again IPSEC software, that is no doubt a thing! But it's no less a thing for OpenSSL.
I don't understand how you manage to get to "IPSEC is less open than TLS", since they're both equally open.
Not IPSEC in itself, but the full stack (tunnel+encryption) implementation in (for example) macOS is completely closed. You could go for something like StrongSwan, but then you lose the advantage you mentioned, namely OS-integration.
https://news.ycombinator.com/item?id=13221923#13223326
What's more frustrating about claims like this are the premises that suggest IPSEC is somehow unknowable. IPSEC is far better studied than OpenVPN is, and its underlying protocol is simpler than TLS (which, of course, NSA is also routinely accused of having tampered with). More importantly: these are protocols, not ciphers. Not only can we read and simulate and test them, we can in fact prove things about them computationally.
I don't know how to articulate the succinct and conclusive argument that you're "not even wrong", but that's the territory that claim lands you in.