Krebs reporting comes from a potential conflict of interest in that the person who might have been trying to blackmail was also the source. Defamation is not really the issue then because the source was pointing at a security problem which they happened to also be the cause of. The entity that hired this person was...Ubiquiti! Hence, it is not really defamation AS SUCH. Rather, if anything, it was true but maybe blown out of proportion to get a larger sum of money from Ubiquiti. We don't know how much info the person got their hands on, because Ubiquiti would be to blame for that, wouldn't they?
So, ultimately I think taking down the articles is a mistake in the sense that they reported on a problem either way with Ubiquiti and security. Take off the ad revenue from those articles, and issue a modified retraction on the conflicted interest the source held as a correction. Use it as a cautionary tale on "Sensationalism" and "not always knowing what the hell someone is doing when they report a leak" and move on.