Aliens arrived on Earth and immediately wiped out many social and economic institutions while abducting members for 'reeducation.'

Once finished, they sent a message:

"People of Earth, we bring to you technology that will cure disease, feed everyone, and replicate anything!"

"Why did you attack us first?"

"We do not attack. We purge. Your old obsolete system forced individuals to struggle and to seek an advantage to survive."

"We have laws and regulations."

"Negative, Earthlings. We've learned through our explorations the slate must be wiped clean because it only takes a few to 'poison the well' as your idiom goes."