Okay, but your original claim was:
> Anonymity is the unique aspect of open source that opens the door for malicious activity without consequences.
If you'd like to amend to something like
> Anonymity, which is in play for most FOSS and a decent chunk of proprietary software, opens the door for malicious activity without consequences.
Then I wouldn't strongly disagree. I'm still a little skeptical, because people keep finding backdoors in non-FOSS software/firmware, of course, but it'd at least be a defensible claim. I'm only really objecting to the notion that this is unique to FOSS.