Agreed. But I care a lot more about what my government does to people who break the rules than I care about people breaking minor rules.

Agreed as well. But the question is punted down to how do you decide if someone is breaking minor rules or major ones instead?

AFAIK, US usually resolves that with courts (in this case Immigration Court). That requires a court date which is not as quick to come by.

The way to improve the situation for the future is to introduce changes to the law to allow voluntary deportation for anyone who's not a wanted criminal — but the laws are what they are, and I wouldn't want immigration clerks to have the full power.

Court is not the only way. How many people do you know who got thrown in jail for a minor speeding offense? The system is plainly capable of distinguishing between “needs to go to jail until they can see a judge” and “can go home” cases. This one is just silly, though: it’s “must go home” combined with “can’t leave.”

You can have a system that treats people humanely. We choose not to.

You are not wrong: I am saying that the laws could be improved to clearly define how immigrants are treated and to offer them a default option of "voluntary deportation" at their own cost.