Quit calling them concentration camps. That's ridiculous and hyperbolic.

It walks like a duck and talks like a duck.

  No one forced people to cross the border illegally,

It depends on how you look at it, really. There weren't any individuals forcing these particular people across the border, as such, but due to the terrible living conditions south of the border they were indirectly forced there. Some of those conditions are the direct result of US policies and actions in Central and South America.

  whereas Jews were rounded up and starved to death.

People are starving to death in these camps.

  By your logic, all prisons are "concentration camps".

Not all prisons are run in the way these camps are. I object to any prison run like these camps are too.

  If you don't want them held until trial, what should we do instead? 

Short term they should be held in humane conditions, trials should not take months and instead take weeks at most, families should not be separated. It's not rocket science. Take some of the money you're burning up every day and spend it here instead (and on other things that improve the lives of people).