I would not find it irresponsible. There is no reason to not talk and think about such ideas in my opinion. I think one of our problems is that we don't normalize death or talk about it really -when death is a normal thing that happens in one way or other of its various forms to every human. And suicide is part of that - it is not implicitly wrong or whatever - that is a value placed on it that is not necessary and is not correct.
The therapist I hired said she thought most people have an exit plan - not to use but the idea of having it keeps them feeling safe. I have read all the final exit books - not because I am looking to go now but so that should something befall me where that is my best option - then I have a base. Talking about it with other people I think can lessen the fear and stigma around the idea that almost everyone has some notion of it. I think the tragedy is that we can't talk about it because of fear of discomfort.