We need more people to prioritize "doing the right thing" over "getting promoted", not fewer.
I never encountered a criminal violation though, so I don't know what I would do, if I would I think I might just tipped HR anonymously and if my boss would like to take me down with him / her, I'll just deny frivolously. Luckily I have a great boss and a great company, but I'm telling you, even the worst bosses and companies still want to be good ones, and if you choose how to give feedback in a way that will not sound too critic, you will win.
I used to think it was important to "tell the truth" by which I meant saying the things I thought were important to say. In the end, I recognized that was more about me and my feelings than anything.
Now my goal in bringing up some unpleasant but important thing is to make a difference. If I'm going to make a difference, saying the truth isn't the important thing. It's getting somebody to listen to the truth. That is definitely an art.
The trick is to figure out if its worth it or not, that usually boils down to the the employer.
It wasn't worth it.