In short, the conclusions reached in philosophical disquisitions do not travel. They do not travel into contexts that are not explicitly philosophical (as seminars, academic journals, and conferences are), and they do not even make their way into the non-philosophical lives of those who hold them. The fact that you might give one set of answers rather than another to standard philosophical questions will say nothing about how you will behave when something other than a point of philosophy is in dispute.
For one thing, I think this is somewhat of an overstatement. I've had students tell me that my ethics classes, in particular, have affected their thinking in what they saw as behaviorally significant ways. I've had students tell me that discussions of animal cruelty have caused them to adopt vegetarianism, or at least to moderate their meat-eating or to seek out less cruel alternatives. I've had students tell me that discussions of abortion have caused them to see a complicated (and interesting) set of issues where before they saw an easily-resolved black-and-white issue with a bunch of moral monsters on the other side, and that this would cause them to be more sympathetic and nicer to people with whom they disagree. I've had students tell me that discussions of Rachels & Rachels on cultural relativism or Socrates on the divine command theory have caused them to seriously rethink their initial confidence in these moral outlooks (even if they didn't ultimately reject them).
Now, I don't see it as my role to try to talk people out of stuff like eating meat, conservative positions on abortion, cultural relativism, or divine command theory. I see it as my role to try to talk people into having more thoughtful views on these things. It is one thing, for example, to be pro-life because you believe that life begins at the moment of conception and that anyone who disagrees is depraved and that anyone who would act on that disagreement is a cold-blooded murderer; it is another to believe that abortion is wrong, but whether it is wrong depends on when personhood, not life, begins, and that reasonable people disagree about when that is and whether the status of the fetus is relevant at all. I think that's a significant change; I think that this change is likely to result in behavioral differences where the rubber meets the road; and I think that's a victory for philosophy.
Fish is, of course, addressing Paul Boghossian's recent discussion of cultural relativism. Fish says, "When it’s not the game of philosophy that is being played, but some other — energy policy, trade policy, debt reduction, military strategy, domestic life — grand philosophical theses like “there are no moral absolutes” or “yes there are” will at best be rhetorical flourishes; they will not be genuine currency or do any decisive work. Believing or disbelieving in moral absolutes is a philosophical position, not a recipe for living." In this way he (seems to) argue that there is a clear and important sense in which the results of philosophical reflections (or, at least, those concerning moral absolutes versus moral relativism) do not matter.
My experience in the classroom suggests a different lesson. It seems to me that people who cultural accept relativism typically do this without thinking carefully about what the view says or what its moral implications are. It seems to me that when certain counterintuitive implications are brought to their attention, they typically realize that they do not accept them, and that they did not in fact accept relativism in the first place. They might (initially) describe themselves as cultural relativists and they might claim to accept the central thesis of relativism, but on reflection they don't accept any of its consequences and they think the main argument for the view is badly mistaken. They were just trying to be nice, and they thought that adopting cultural relativism was the nice thing to do. In my experience, it is unusual for people (even people who describe themselves as cultural relativists) to deny that there are moral absolutes (even if, in certain contexts, they would say they do), and this is why you don't normally have to say that there are moral absolutes, and why you don't normally get anywhere when you do. It's not that the conclusion didn't travel; it's that the conclusion traveled without everybody noticing and is there already. Philosophical conclusions travel incognito.
We saw something like this here in the late spring/early summer. In a very long comment thread, a commenter persistently argued that philosophy, unlike empirical science, doesn't generate genuine knowledge (or something like that), but would persistently and at every turn defend this thesis by making reference to what were clearly non-empirical philosophical theses that were essential to the position.
And finally, if Fish is really right that philosophical conclusions don't travel, isn't that more of a criticism of the people in whom they fail to travel than the philosophical conclusions themselves?