His article is specifically about pretend free/open source licenses that restrict what software can be used for. But the conclusion applies to similar behaviors around the entire free/open source ecosystem like conferences: it will just drive participants away and strengthen the position of proprietary solutions instead.
I don't actually know his position on this, but mean to communicate I see the use of free software and the sponsorship issue as separate issues.
(Signed, someone who absolutely does not want military contractors in their community, but feels that a license is the wrong place to enforce that.)