They did apologize for this and as you say, disclaimed involvement or interest in such a plan. [2]
[1] https://wikileaks.org/IMG/pdf/WikiLeaks_Response_v6.pdf
[2] http://www.forbes.com/sites/andygreenberg/2011/02/11/palanti...
But also, the branding of the presentation does not reliably indicate the origin of the specifically offensive bullet points (most notably the "Potential Proactive Tactics" slide), nor whether the contents ever progressed past trial-balloon status.
In particular, coverage by Greenwald [1] (working from more email thread context for which I can't find a current online source) identifies HB Gary principal Aaron Barr as the verbatim source of some of the most-aggressive anti-Greenwald language.
So I can see that someone at Palantir was coordinating with the other entities and leading the document-prep. But they also cut-and-pasted material from the potential contract partners, including vague proposals outside Palantir's focus, that may never have been approved or presented.
I'd ascribe those bullets to Palantir itself if that deck was in fact ever presented to a client. We don't know if that's the case. If instead that text just bounced around as a discussion draft (including their more-aggro partners), but went nowhere, and was eventually categorically disavowed... then it's a stretch to say that the company or its leadership actually advocated those steps.
"So apparently, if Palantir’s new version is to be believed, a 26-year-old engineer went off on his own and — without any supervision or direction — participated in the development of odious smear campaigns intended for two of the nation’s deepest-pocket organizations (Bank of America and the Chamber), potential clients which the emails repeatedly emphasize would be very lucrative. I’ll leave it to others to decide how credible that version is, but I will note that several facts undermine it: ..."
"The leaders at the very top of Palantir were aware of the Team Themis work, though the details of what was being proposed by Barr may well have escaped their notice."