There is this thread (
https://bitcointalk.org/index.php?topic=2680267.0), which is also full of statements, but without any proof or link. Already the OP choose a name, which make the content doubtful, and the headline doesn't count at all for scientific proofs. It is good to start a discussion, but luckily this post remained unanswered.
This thread (
https://bitcointalk.org/index.php?topic=288545.0) has many links to SHA256 and NSA, but it doesn't become obvious, if there is a backdoor or not. It also looks more like speculation.
In the first topic, the guy was just giving his own opinion. It's a conspiracy theory that is around for a long time now. Maybe a friend of Alex Jones. You can read conspiracies about anything on the web. As for the document the member was talking about, this is the report from 1996.
http://groups.csail.mit.edu/mac/classes/6.805/articles/money/nsamint/nsamint.htmIn the second topic, i would say nobody here has enough knowledge to give us a proof. I don't say it's impossible Big Brothers NSA has broken already bitcoin, but if a single proof existed, it would be public all over the web