Ask them to lead the clean up it themselves. This let's you acknowledge their good intentions and doesn't feel like you are throwing them under the bus behind their back (bad analogy).

They screwed up, but this lets them look responsible and self accountable. There is no cure for bad management, but with decent management the friend will be more embarrassed than anyone would be judgemental - screwups happen, coverups or ignoring them is the thing that is far worse.