You can definitely make the case that the large moderation infrastructure fielded by gigantic social media companies has been anywhere from imperfect to outright irresponsible.
The difference is, there was actual moderation. Parler, a tiny (2 orders of magnitude tinier than Twitter) appears to have had no moderation infrastructure at all.
Even the data in your first reference seems to suggest that Twitter alone has probably moderated more accounts than Parler has actually had.
"The Islamic State of Iraq and ash-Sham (ISIS) continues to use social media as an essential element of its campaign to motivate support. On Twitter, ISIS’ unique ability to leverage unaffiliated sympathizers that simply retweet propaganda has been identified as a primary mechanism in their success in motivating both recruitment and “lone wolf” attacks." [2]
Apparently US authorities were happy to want Twitter to keep those accounts alive for some time as they could use them to track activity - the point remains it's wrong to the point of naive to believe that these decisions are not political.
Facebook was enabling genocidal activity [3].
It's incredibly hypocritical to look at the historical activities of ISIS on Twitter, Facebook and all of these platforms, and then to hear about the 'political violence' caused by Parler.
I don't like Parler, the hypocrisy is staggering.
[1] https://en.wikipedia.org/wiki/Use_of_social_media_by_the_Isl...
[2] https://journals.plos.org/plosone/article?id=10.1371/journal...
[3] https://www.nytimes.com/2018/10/15/technology/myanmar-facebo...