Same with guns. The police are okay with gun ownership because they have the right to gun citizens down. Not to judge, but that's the balance.
Same with why we tortured. It counterbalances their vulnerability to secrets. If torture didn't work, Kiefer Sutherland would never have gotten anywhere. But if everyone were against torture, the show wouldn't have existed.
They have an answer to locked doors, suspects with guns, and terrorists with secrets that -- at minimum -- make sense to them regardless of their effectiveness or consequences to society or our ethical reputation.
The main problem with encryption is there is no workaround. There is no counterbalance. The lock is unbreakable, and there is no one to shoot or torture when all they have is the device itself (and no one to torture always, if they're abiding by the law).
This scares law enforcement. This whole campaign is driven by fear, but they cannot admit fear, so it's all rationalizations and confabulations -- which work by the way -- hence they're keeping at it. And when those with power empathize with this fear in between the lines, they will sign off on these lies.