McKinsey is in the business of reputation laundering. They start the process by building up reputation. They hire from prestigious schools, have prestigious customers, make themselves a household name for the people that matter.
Then when you need someone to make an unpopular decision for you, or take the blame for a project failure, they swoop in and take you money in exchange for taking the reputation hit. It's fine, they know how to grow more reputation when necessary, and everyone at your org or in the media if the situation calls for it, points to them and says "what a bad/stupid/down right evil decision McKinsey made!" while remain the responsible person who tried their best by hiring what you and your peers thought was the best.