I have tried, but have not found a way to respond to this question that is not opinion based. By their nature, a person's ethics are just that; a person's ethics. They are usually deeply held, personal beliefs. Other words for ethics might be morals, values, conscience, etc., again, these are not necessarily universal in their importance. They are personal. In addition, how a person behaves in the workplace, is still usually going to reflect their own personal beliefs.
The main point that jumped out at me from the question, was that it was asked at all. The fact that it was asked, means "ethical obligation" is something important to the person who asked the question. Not everyone would give it the same amount of thought, or priority. The fact that it was asked in a public forum, as though there has been some real conflict about what action to take, means it may be weighing rather heavily on Mr. Collings.
My answer would be to do something we don't do nearly enough, and that is to think things all the way through, to their various conclusions. For example, what would a "worst case scenario" look like? Or a best case scenario? Then, as Mr. Christianson suggested, you would have to ask yourself if those conclusions were ok with you, and matched closely to your own, personally arrived at value's. If yes, then you're good to go. If not, you may need to look further for your answer.
Also keep in mind that what meets the legal, or professional definition of ethical, or unethical behavior, is not always going to meet our own definition of those same terms, nor should they. In fact, it has been said that facing these kinds of moral dilemmas, is what builds character. To be honest, I just made that up. It's actually just my opinion.