There’s nothing inherently wrong with having a conflict of interest. It happens all the time, and the key issue is disclosure and how you manage it.
Sometimes it is perfectly fine for the conflict of interest to exist, provided there is disclosure to the relevant parties. However, accusing someone of having a conflict of interest after they have determined that they don’t is a surefire way to spark a reaction. No one likes to have their integrity questioned, but sometimes people are blinded to their conflicts as they pursue self-interest.
In light of the AFL and Amber Harrison sagas, the disclosure antidote seems to be where the consensus is at with office relationships. Of course, a conflict can exist when an office relationship starts, but just tell your boss and make sure no company resources are misused, favours granted or unfair treatment meted out when the relationship finishes.