However, at the point where you want to say someone should or should not do something the subjective morality comes back to bite you (saying curi's trick was underhanded). I think this is curi's point.
All you can really do with subjective morality is describe your rationale for why you do what you do, and hope the other person buys it. Even that is inconsistent because you are motivated by the thought that the other person should do something.
Curi, while it is true we start from first impressions, either our goals have to be mutually independent, or they must have a common foundation. Otherwise they end up contradicting each other. That's the point of moral philosophy, and what I meant by justifying moral intuition.
You can also remove contradictions locally if you find any. If you want, you can say that is based on the common foundation "if two ideas contradict, at least one is false". But the point is, you see a contradiction, you know at least one of the ideas is mistaken in some way, so you know there's room for improvement there, until you come up with some changes that remove the contradiction.
But certainly seeing as much of an "ultimate purpose" to aim for, as we can, is helpful. We have ideas of parts of it. Creating knowledge is good, and destroying it is bad. Freedom is good, and controlling other people is at best a temporary stopgap measure, not an ideal. Cooperation or indifferent tolerance is good, and violent conflict is bad, both because it's destructive, and because it's not a truth seeking process. Settling for less is not ideal, and anything that puts pressure on people, or creates incentives, to not strive for all we can, is bad.
Some of these assertions have directly applicability today. For example, the common perception that striving for more is "hard" (unpleasant) indicates something or other is going wrong. Or there's the idea that life is about compromise, which is essentially settling for less. People don't just fail to find a with to proceed with no downsides, but often people don't even try, and assume such things do not exist. The ideas in our culture which cause these attitudes clearly have room for improvement.
"moral philosophy has to do with determining the end"
Yes, but that's not all. How to approach goals, how to solve problems and correct errors, what sorts of policies for how to live your life are effective, are also very important topics (and perhaps more accessible and directly useful). One of the critical ideas here, I think, is that all these things depend on knowledge. How do you approach a goal? In general, you need to create knowledge about the goal and how best to approach it (and also whether it's worth accomplishing, in case it was mistaken). To solve a problem, you have to figure out how to solve it. (And if implementing the solution is hard or unpleasant in any way, that could be avoided with still more knowledge of how to solve the problem in an easier way.) To correct errors, you have to create knowledge of what ideas are in error, and what would be better ideas. And so on. And therefore, anyone who is seriously interested in morality ought to study epistemology.