If an American family moves to Europe, their US citizen 7 year old doesn't have a right to stay in the US without their parents.
If immigrant parents move out of the US (because of deportation) their US citizen 7 year old isn't being denied or deprived of any right by being sent with them 🤷♀️
The American family's 7 year old can't demand a non-citizen relative be imported to care for them which their family is out of country, and neither should the immigrant family's 7 year old.
I am personally an open boarders guy, but this doesn't strike me as particularly unreasonable as long as they're just being deported and not sent to supermax dungeons.