This is too closely related to my interests for me to resist posting on.
First, a few distinctions in terminology should be made.
There is a difference between morality and ethics. Morality is one's personal view of right and wrong (What I estimate is right for me). Ethics is a social view of what is right and wrong (What I estimate is right for others). The two often do not match up (I estimate that it is immoral for me to buy products from companies like Chick-fil-A. I do not estimate that it should be a rule that no one buys from such companies.).
There is a difference between subjectivity, inter-subjectivity, and objectivity. Subjectivity is the relation of my personal perspective to myself (Seeing people throw up makes me want to throw up). Inter-subjectivity is the relation of people's perspectives to each other (Most people feel sick when seeing others throw up). Objectivity is the relation of observable reality to everyone's perspectives (People who have had x experience report, on average, an x% likelihood that they will throw up when seeing others do so).
We can never truly have an objective perspective on direct reality, because we are limited by our personal subjective access of the world.
Whether or not ethical claims can be identified as more or less "true" (recognizing epistemological limits) or "right" than others can be determined by the same process by which we identify scientific claims as more or less "true" or "right". To say that all ethical claims (and moral beliefs) are equal and outside of truthful evaluation is to say that science is meaningless and that progress is impossible. We know this to be false.
What should be said is that every claim is always possibly false or wrong, no matter how much evidence there is behind it, because of our limited knowledge and ability to know. Even so, we can have varying degrees of certainty (or confidence) in the truth value of claims.
What people who discuss morality and ethics often fail to do is recognize the difference between talking about specific moral/ethical claims and general "rules of principle". That is, they do not factor in context. This is the equivalent of discussing science as though there is no such thing as specificity of hypotheses. It's like talking about school success without talking about contribution factors. (Oh, Hi! Nice to see you NCLB.)
We may not have the ability to evaluate claims in absolute terms - much less the ability to evaluate broad claims in absolute terms - but we can and do evaluate claims in specific terms. When the evidence for specific claims piles on, people make leaps to similar general claims. This is not a scientifically justified move, but the jump does have more backing than remaining with old general claims.
Consider the vague case of democratizing the public vote (removing poll taxes, making polling places easier to reach, etc.). We may be wore off now because of the amount of uninformed voters, but we are certainly better off than having control solely in the hands of a privileged group.
If that is too vague, then relate that case tot he case of abstinence-only education vs comprehensive health education. We may have crammed too much information into a small bracket of time in many comprehensive programs, but these programs are far better than the negative results of abstinence-only education.
And what is out measure of "better off"? The increase of feelings of pleasure and the decreases of pain - a consequential analysis.
While we may not be able to clearly identify the benefits and gains in terms of consequences in middle-sized change, we can see them clearly in specific scientific research and in at-large social change.
There is progress. We are more ethical - better off - than humans were in the past, on average.