If they are seizing and searching your laptop, it isn't because you're violating ITAR or carrying dual-use spreadsheets. There are few legitimate reasons why the authorities should be at all interested in the data on your devices when you are entering an area where both free speech and privacy are considered rights.
Among other goals, they are assembling profiles on dissenters, to be used against them later. If you give them something that appears legal but still potentially embarrassing, that's disinformation that might save you from a stronger attack later.
This differs from a narcotics search in that having data on electronic devices is not a crime. They could not perform such a search anywhere but at a border crossing.
