Yes, there is- because "the harm or suffering of others" is still entirely dependant on an observer- the one experiencing the harm and/or suffering. "Suffering" is entirely in the eye of the beholder, and the exact same thing that causes one person to suffer may benefit or even please another.
Detonating a stick of dynamite may cause differing amount of damage depending on where it is located. In some situations, such as in the mining industry, detonating a stick of dynamite may even be beneficial.
This does not make the damage from detonating a stick of dynamite subjective. It only makes it situation dependent.
Likewise with morality. Some people may greatly enjoy being bound in leather and lightly whipped, others may find it a traumatic experience. Whether or not the subject of this experience finds it pleasurable or traumatic can, in theory, be determined objectively through a brain scan while being subjected to this treatment. So the outcome, pleasure or suffering, is an
objective result of this action, regardless of whether or not you actually know which outcome is being achieved.
So if we define morality as choosing to act in a manner intended to minimize the harm to or suffering of others, then binding people in leather and lightly whipping them without their consent is not moral because, while some people may find it pleasurable, others will find it traumatic, and you are, by any objective standard, acting in a manner likely to cause suffering to others.
Whether or not an action is likely to cause harm or suffering in any given situation can be objectively determined by empirical experimentation. For example, you could punch a thousand random people in the face and record the result to empirically determine whether or not punching someone in the face causes harm or suffering. The outcome of such an experiment would yield objective results, and even if a small number of people actually enjoy being punched in the face, this would not change the fact that it has been proven that punching someone in the face is an action
likely to cause harm and suffering, and therefore someone attempting to act in a manner intended to minimize harm and suffering would not generally go around punching random people in the face.
And you do that by measuring conduct against the standard you have decided is what is "moral". This standard exists in your mind (and the minds of those that happen to agree)- it does not exist independently of thought or an observer.
Some people might set the standard for measuring the height of a mountain as the distance from it's highest point to the center of the earth and conclude that Chimborazo is the tallest mountain, while others might set the standard for measuring the height of a mountain as the distance from it's highest point to sea level and conclude that Everest is the tallest mountain.
These standards exists only in people minds, and do not exist independently of thought or an observer.
But using the standard of distance from the center of the earth, Chimborazo is
objectively the tallest mountain. Using the standard of from seal level, Everest is
objectively the tallest mountain.
Morality may simply be an abstract concept, but that does not mean that action cannot be objectively moral or immoral. Deciding on which standard to use to measure morality is like deciding on which standard to use to measure the height of a mountain. Different standards may yield different results, but the results yielded by those standards can still be objective.
Except distance exists independently of an observer. One's behaviour, and the values and priorities used to measure them, do not.
Tell me, what is the distance of a tree?
In order to determine an objective measure of distance, you need to define a point of reference from which distance is measured from.
In order to determine an objective measure of morality, you need to define a point of reference from which morality is measured by.
I'm attempting to use
acting in a manner intended to minimize harm or suffering as a reference point with which to measure morality.
Going around beating-up random people is contrary to acting in a manner intended to minimize harm or suffering, and is therefore immoral when measured from this reference point. It doesn't matter who the observer is, or if there is no observer at all. The fact that this action is contrary to the behavior of a person acting with the intent to minimize harm or suffering is true regardless, making this
objectively immoral behavior.
If these are morally true for everybody equally, independant who does them, if everybody agrees these are unquestionably what is always "right" and/or "wrong"- why do they still happen?
Because not everybody chooses to always act in a moral manner. Where's the confusion?
As for disagreements as to what does or does not constitute moral action, not everybody uses the same standards for their basis of morality.
And as for the Aztecs, if their beliefs about human sacrifice being required for the rain needed to grow crops and avoid vast amounts of death and suffering by starvation had been correct, then it could be argued that their practice of human sacrifice might have been, on balance, the right thing to do. Their actions could be regarded as objectively moral for a universe where rain is dependent on child sacrifice.
But thinking over that example, the "intended" part of my definition for morality may be a flaw. Perhaps We should define moral behavior as simply:
Acting in a manner likely to minimize harm and suffering of others. In this way, people may believe themselves to be acting morally, when in fact they are not. I may disagree with a lot of what you have to say, but arguing with someone holding strong contrary opinions is a great way to refine your own understanding and position.
) Check out this wiki section on "pitch inflation" if you'd like to get a short primer. 
