Not wishing to extend this thread further, but ...
There are conspiracy theories out there that the NSA is involved with bringing systemd to Linux so they can have easy access to *"unknown"* bugs - aka backdoors - to all Linux installations using systemd *[1]*.
They're conspiracy theories, and that's it. The bottom line is that in general people don't like not understanding things and when they come across something they don't understand they create a mythology around those things to rationalise their non-understanding. Factor in to that the general mindset of Linux hackers/admins that they must know and understand every part of their system and you create the perfect environment for such theories to grow and blossom.
Systemd is complex; it's implementation was badly handled on a social level. Nevertheless it is open source. It is highly unlikely that the NSA, or any other agency, would risk putting in backdoors to code that could be audited by Joe "random hacker" Blogs, let alone that might be discovered by hostile agencies.
There is no doubt that most security agencies have a long list of zero- day exploits in their toolbox - I would hazard to suggest that they wouldn't be doing their job if they didn't! But I seriously doubt they would commission exploitable code in something that is openly auditable.
P.