Of course it is. Just as big, small, hot, cold, smart, stupid, light, dark, fast, slow, and any other myriad of spectrums are all "meaningless in any objective sense". They all glean meaning from relations. We can't look at any object and objectively determine if it's big or small, for we would get a thousand different interpretations from a thousand different perspectives. However, if you compare a mouse to an elephant and ask "Which one is big?" anyone in their right mind would say the elephant is big, compared to the mouse. Same with hot and cold, nothing is objectively hot in itself, but compare a fire to an ice cube and ask which one is hot, and the distinction becomes very clear, and very objective within the relational context.
It is no different with morality. When we ask whether something is right or wrong, nothing is right or wrong in itself, it is only right or wrong in a relational context. Does a specific act realize ends that we desire? This is the only litmus test for whether or not an act is right or wrong. If a society desires the safety of its citizens, murder is wrong because it does not realize this end, it is harmful to the end. However, if a society was overpopulating at a dangerous pace and was in threat of running out of resources and everyone dying, and thus they desired a drastically smaller population lest they all die, then murder would become appropriate, as a means to decreasing the population perhpas by killing everyone over a certain age. Who are we to say that is wrong? We are only people with differing desires and ends in mind, that is all.
Whenever you say that "X is wrong" or "X is right" you are really exposing those ends that you desire, and you are labeling things conducive or not to said ends. To try and tell people there are absolute morals is to try and tell people there are absolute desires, that everyone does or should desire in the same manner and same degree. This is utterly ridiculous, and thus appealing to absolute notions of right and wrong is utterly ridiculous.
All moral rules must be tested by examining whether they tend to realize ends that we desire. I say ends that we desire, not ends that we ought to desire. What we ought to desire is merely what someone else wishes us to desire.
-Bertrand Russell