Border searches aren't arbitrary when done for the purposes of border security and applied to travelers in a non-arbitrary way. It's pretty clear that CBP agents have a wide discretion to search people at their own whims i.e. arbitrarily.

>that the government does so lawfully

There are many legal question in this case, it's not clear the government acted lawfully. If he'd have arrived in a different federal court district, the search was unlawful because precedent says they need reasonable suspicion.

Not to mention this was a pretext to gather warrantless evidence for the FBI for a domestic investigation and nothing to do with securing the border.

>Antagonising law enforcement in this situation is not a smart move

Not what he did.