I am not saying you would, but if it lead to something like a more serious incident or scuffle you could be viewed as the agitator when it comes to responsibility etc.
Nothing wrong with being proactive in matters that are yours, however some may see this situation as none of your business and to a certain extent the law backs that up, if the crew asked you to intervene, its a different story, how many times has the question been asked "why didnt you leave the matter in the hands of those whose job it was"? In some jurisdictions such action could result in a civil suit alleging negligent infliction of emotional distress by the very person you feel is impacting on your safety, at the end of the day you should be aware of the possible outcomes of your actions and the liabilities they may invoke! On the other hand, I am not aware of anyone who has been in trouble for asking someone to do their job!