I like to think of it in terms of house keys.

It's one thing if a border guard inspects your house key you brought along, analyzes for dangerous substances, drugs, etc.

It's another if they clone that key and have someone drive out to inspect your house with it.

To me, your house in this scenario is your entire collection of private data accessible online / remotely (finances, taxes, possibly the private data of others -- possibly even portals to HIPAA/other PII data of a more commercial nature).

Assuming you agree that it is unfair to let the border search data outside of the phone, then it gets still more problematic.

One of the tricky aspects here is that it seems you can be detained / intimidated if you refuse to decrypt / unlock your device (as a US citizen re-entering your own country). I think you're getting at the idea that the phone/laptop is a physical device and should be searchable like any other object -- and, I think that's fairly reasonable. The problem is that the border guard can also "compel" you to decrypt that device / log in to it if you've put these measures in place. People have been forcibly detained for refusing to cooperate [1], even being put into a chokehold [2].

I respect that some amount of extra search power is required at borders -- but that power must be reasonably scoped (and in this case, I'd say it is not).

[1] http://www.cnn.com/2017/02/13/us/citizen-nasa-engineer-detai... [2] https://www.nbcnews.com/news/us-news/american-citizens-u-s-b...