No? You're not complicit with fraud if you suspect someone of fraud but don't go public with your suspicions. I don't think that's up for debate at all tbh.
Huh? You think there's a duty to publicly call out mere suspicions of fraud? I would argue there's the opposite -- people are hesitant to go public with any accusations because of the very real threat of being sued for defamation/libel.
There are very few true obligations to report in the US. All I'm aware of are tied to specific occupations/licenses.
