I am not a conservative and I make the same argument. I also fight for civil rights and protections of the Bill of Rights on a near daily basis in front of the courts. I have 3 cases in front of the 8th Circuit right now. I would demolish the War on Drugs and the War on Terror this instant if I had the power to wish them away. Mothers Against Drunk Driving scares me more than Al Qaeda. I absolutely oppose FISA "courts" and warrantless wiretapping. I strongly oppose the militarization of police (just ask them) and the campaign of drone strikes going on abroad. Indefinite detention of anyone, but particularly American citizens, is per se sickening and reprehensible.
I also wouldn't be so quick to say that it is the conservatives who are eroding the Bill of Rights in the name of safety. The Obama administration has taken all of the Bush policies that violate civil liberties and made them worse or normalized them.
Just last week he signed the NDAA extension which included indefinite detention provisions for American citizens. This week he is signing (has signed?) the FISA extensions.
And it is worth noting that both of those bills came out of the same Senate committee...the one headed by Dianne Feinstein.
And frankly, I would pose to Mr. Friedersdorf that people like him are paving the way to rights limitations. Rhetoric and action on the 2nd Amendment to restrict, normalize restriction on rights generally. We start framing the topics around "Need," and "reasonableness," and "appropriate regulation." It is that framing that killed the 4th amendment. It is that framing that is killing the 5th. It is that framing that is firing shots across the bow of the 2nd.
The main difference between the 4th, 5th, and 2nd Amendments is that the 4th and 5th Amendments are often academic or theoretical to many people. Most people aren't searched routinely by the police. Most people haven't had to go through asset forfeiture proceedings. Lots of people actually own firearms and they have a personal and financial stake in them.
Regardless, I think it is also worth noting (if even anecdotally) that places with tightly regulated firearms also seem to be not giving a shit at all about the fourth and fifth amendments either. New York City, home of Mayor Bloomberg and notoriously stringent gun laws (just ask him), is also home to arguably the most abusive police force in the country. NYPD performed 700,000 "stop-and-frisks" in 2011. They found contraband in 2 percent of those stops. It really is a police state.