Part of what the Cs have to consider is even though (I'm assuming) both parties may have said it was consensual, when someone in a position of power has sexual relations with someone on their staff there's always a slippery slope. Especially in this #metoo era. The woman could always come out later and say she had been coerced (for all we know she could have), and file a lawsuit, and I think she would have a great chance (even if she hadn't been, I think he's opened himself up and put the Celtics in a position where they could face a future lawsuit). That's why inter-work relationships, especially with your staff, are never good things. Maybe 30 years ago when nobody gave a stuff but not today. Really bad judgment from Ime. It's always tough picking between your job and your love (or lust) but with that power dynamic, not to mention the fact that he was violating organization rules, he was playing with fire and he only has himself to blame for getting burned.
I'm not sure what kind of precedent there is in the league we could look to for guidance as to the penalty. Different people will have different opinions of it - some will say it's no big deal, they're two consenting adults, let them play hide the sausage if they want as long as our team keeps winning who cares. Others will think that Ime abused his power to have this intimate relationship with a staffer. Then there are the folks in the middle. But what matters is not our opinions but what the Celtics organizational rules are, and what the penalties for violating that would be. And from the reporting it appears that there are rules against it, and so having workplace affairs violated those rules. Just a matter of working out the punishment then.