Will this phenomenon simply continue to escalate until finally something horrible happens? Hopefully I am underestimating the sanity of politically-charged gun owners.
[UPDATE: At TPM, Josh makes good sense on this issue, concluding: "...put me down as not believing we should allow the brandishing of firearms in proximity of the president as an acceptable way of expressing opposition to the president. Shouldn't this be obvious?"
But the next logical point has to be heard as well. The reason the White House will *never let the Secret Service* establish policies targeting that kind of behavior is a political one: Obama will not want to be seen as fulfilling the prophecy of the irrational right that said he will take away their guns. If one nutjob legally carrying a gun in a protest zone is detained or forcibly disarmed, firearms will be everywhere and we won't hear the end of it.
The good news is that this problem - political as it is - has a very reasonable and easy political solution: some Republican who is respected by gun nuts needs to be the one to come out against this kind of display and demand the Secret Service take additional protective measures by expanding the no-gun perimeter in public gathering places around the President at events. The bad news is, yeah I can't think of who would do it, either. But the fact that nobody on the other side is raising this issue as a matter of essential security - protecting our President, for goodness sake! - is a pretty good indicator of the current Republican commitment to disunity.
Say what you will about even the Clinton years. I don't remember armed protestors showing up with impunity. When did this become ok?]