Illegally entering the country is a civil misdemeanor. If that is someone's lone crime it's like throwing people into Rykers for a speeding ticket.
I'm no lawyer but I believe a misdemeanor is a crime. As a matter of fact I don't think there is any such thing as a civil misdemeanor.
Anything he is accused of is completely irrelevant to the concepts of due process and cruel and unusual punishment. If he has done what they accuse him of then he should be tried, convicted, spend the time in jail, then deported. If that’s “foolishness” to you then so be it.