I think (personally, mind) that this is a strawman argument. Comparing guns to privacy is as valid as comparing speech & religion rights; i.e., it isn't. Still, I'm going to give you a little info dump here because I care (about human rights).
I have a right to carry a gun in any sane (number declining regularly, sadly) country on this planet because I have an inalienable human right to defend myself, and because technology cannot be made to go backward.
No matter how much the governments would like to take guns away from the terrorists, they can't. You stop the sales of guns or the gun manufacturers, the terrorist will go to the hardware store and buy steel pipe in 1 or 2 foot segments, and a hammer. You outlaw the sale or manufacture of ammunition, he'll buy a (then drastically inflated price, but he'll still do it) reloading bench. And that's not even addressing the used markets, OR black markets. Both have been proved to thrive no matter what steps you take against them.
If a man wants to kill someone he will do so with the best tools available to himself whether those tools are legal or not. The only way to protect the people is to allow them a reasonable right to carry. Examples of reasonable limits: door check & lockers for weapons at particularly sensitive places like hospitals, ownership limits on full-auto weapons, etc. Example of non-reasonable limits: mag size limits, conviction for non-violent crime barring ownership, etc.
Moving on to privacy, the governments don't want encryption to stop terrorists. Fact is, and the governments know this, that old-fashioned detective work is the best way to stop actual criminals. Look at the Silk Road case. Everything Ulbricht allegedly (and I think pretty strongly) did was encrypted, and he was on the tech side of things, protected in all sorts of ways. How was he caught? Detective work.
Encryption poses zero threat to governments from terrorists or other criminals. It may make a few cases somewhat harder. I doubt it will make any just case truly impossible. We're very good at training investigators, whether they're called Agents or Detectives.
On the other hand, well implemented encryption promises a lot. It means protection for activists, whether here in the US or in places like China. It means security for the common user, against for example hackers whose motivations cannot be ascertained until after the fact. It means that people who are part of subcommunities that are legal but looked down upon can interact and communicate without fear of harassment caused by a 'digital bystander' outing them.