It's alright to be late!

Once, a few of them came in late. And I said,
"Maybe you think it's alright to be late a little bit, because it's none of my business. And yes, there's really nothing concern me whether you are late, or you are not here at all! I just have to give you some advice as it is my duty to do so. You will be forgiven and there's no impact to you."
And they laughed.
I said again,
"When you are working in the real world, you will hear no more nagging or advice. Because your boss will only say to you,"You are fired!". And that's it. And that's all."
"Would you blame your boss for fired you just because you were late?"
"If you are the boss, would you hire somebody who came to work late?"
You should know what they answered, right?
"Before I leave this room, I just want to tell you: Your business is none of my business, but it is YOUR BUSINESS to decide whether you want to GET the BUSINESS or NOT!"