Ethics are important in the workplace. So important that you should error on the side of caution.
Just because you don’t have evidence that someone did something immoral, doesn’t mean you should ignore your gut when something doesn’t feel right.
Does it seem like they are leaving out details?
Does it seem like they are withholding their sources?
Does it seem like they are reluctant to share information?
These are important signals. Trust your instincts. Call them out or walk away. If you don’t, you'll be sorry down the road.