Everyone seems to think that the Dark Tangent is making a political statement uninviting the feds to DEF CON. Maybe, but there's nothing political in his message. Whatever politics you read into it are those you brought with you.
People who run things, from corporate CEOs to con organizers, learn to keep themselves above the fray. They spend a lot of effort heading off conflict before it has a chance to start. They don't take sides. Those who are wedded to their side are sometimes unable to recognize this impartiality.
A highly visible fed presence is likely to trigger conflict with people upset over Snowden-gate. From shouting matches, to physical violence, to "hack the fed", something bad might occur. Or, simply attendees will choose to stay away. Any reasonable conference organizer, be they pro-fed or anti-fed, would want to reduce the likelihood of this conflict.
The easiest way to do this is by reducing the number of feds at DEF CON, by asking them not to come. This is horribly unfair to them, of course, since they aren't the ones who would be starting these fights. But here's the thing: it's not a fed convention but a hacker party. The feds don't have a right to be there -- the hackers do. If bad behaving hackers are going to stir up trouble with innocent feds, it's still the feds who have to go.
What about feds that are hackers?
"we don't do politics" IS a political statement. Dialectics, you know. Full of traps.
How is this apolitical? Whether it's fights caused by hackers who have been abused (and they have been, the same way everyone has) as part of the event politics, or fights caused by feds attempting to serve warrants (which they would do), it's all about "this group has reason to be angry, and this other group has no reason to do other than swat the angry people except a piece of paper the Justices have used as toilet paper". This is the pre-Stonewall condition, if I might be permitted to make a civil rights comparison. And the number of hackers either does or does not match or exceed the number of feds. So, the feds can either swamp the party, or they can be at risk if they go. The party organizers don't want it swamped.
Make no mistake, even the reasons you say are political. They are based on what the organizers perceive possible or likely reactions based on the mostly libertarian & anarchist hacker culture, and mostly lawful neutral/evil motives ascribed to the members of government ordered and willing to secretly treat them like foreign powers that need to deal with US espionage. Nobody likes that, but feds don't defend their citizens from state-level abuses so their secrecy makes absolutely every one of them suspect.
The motives you cite are based on event/fandom politics, which only came about because of the national politics. This is a political ripple, a judgment that there are people who are so angry that they could form a mob against an unprotected fed, and a judgment that the feds will be much less safe this year if they show.
So, ultimately, your central argument is undermined, but can be made legitimate by saying "not directly political against the feds, but definitely reactive to the mood of the non-fed people participating and the situation's volatility with those peoples' willingness to fight for their freedoms against all enemies, foreign and domestic."
Which makes this a political statement about the hackers, more than the feds.
Robert Graham is correct I think. Last thing DefCon needs are emotional confrontations over political issues.
I agree with Robert that the probable primary motivation for Moss' stand is to avoid unnecessary confrontations during the event.
However, it IS still a political situation. Because the ball is now in the Feds court. Do they come anyway and disrespect the event organizers? Do they come and then NOT LIE about the NSA invasive programs like General Alexander is now proven to have lied in the past?
I also agree with Robert that Defcon is a hacker conference, not a Fed conference. Few people would complain if the event organizers exercised their right to exclude neo-Nazis. The comparison with the NSA is now clearly apt.
There have been talks at infosec conferences before about "the dark side of infosec". Then there was the HBGary Federal incident. It is appropriate to raise these sorts of questions now.
The people dropping out of Defcon as a result of this are people who are effectively proclaiming their support for an oppressive and invasive government. It's not just about "inclusiveness". And that stance will taint them in the future.