When 12-18 members of your staff 'take a single day off', depending on the size of the business, that could shut a company down for a day. Product not made, angry clients, overhead to be paid.
Apparently, you are of the mind that the business exists to give people jobs. Most don't.
From what I've read on this story, several had been employed there for a couple of years, so either the were okay with the pay, or didn't want to look for another job. They were told not to take the day off... that doesn't mean they didn't have days they could take off, it means, for whatever reason the employer need them there that day, and they decided to do it anyway.
Their actions show a complete disregard for the employer, and most employers do not have the time nor income to spend on people who have that attitude.