There are places where I think relativism is true, in that knowledge, truth, and morality exist in relation to culture, society, and /or historical context, and are not absolute.
I think the view you express here is slightly off-base because of the following: culture is a product of intersubjective interactions that generate and reify perpectival opinion. However, that doesn't make culture true/valid relative to the people who create, reify, and apply it. It merely means that culture is always in a necessarily incomplete state of progress toward perfection, which can never ultimately be achieved.
So it's better to regard culture as an attempt to achieve whatever its human creators/practitioners are seeking or doing with it, and avoid regarding it as true/valid relative to the people/identity associated with it.
As a Christian, I see that God's subjective list of morality became an objective task for morality with the Hebrews, otherwise called the Laws of Moses. Though I believe that the Laws of Moses were given to show how inept Man is to live by them; they weren't meant to accomplish them, they were meant to see how they fail, and how they needed God to forgive them of their failure.
True, there is value in observing imperfection and confessing/repenting for it and thus receiving forgiveness/salvation/redemption/sanctification; and that is arguably the main purpose/function of Christ.
But there is also value in deciphering deeper truths expressed within the imperfect cultural/moral tenets that have been generated throughout the ages. E.g. various dietary restrictions may have been inadequately partial and based on agricultural factors and limits in play at the time they were adopted, but the general idea that it is morally/ethically good to restrict diet for various reasons is universally valid.
Dietary restriction, generally, is a subset of the general morality/ethic that humans have the capacity to think/reason and exercise willpower in listening to their consciences and thus put effort into sacrificing certain pleasures/choices in favor of effectuating a greater good that (sensual) gratification, indulgence, etc.
The reason why I said that is the set before you my understanding, which I don't tend to see in terms of universalism, absolutism, or relativism. So the approach, the taxonomic you use is not what I am accustomed to. That's what I'm trying to say.
I find the distinction between relativism and universalism extremely useful and relevant to understanding the struggle between political liberalism and moral liberty. In the case of relativism/liberalism, no natural convergence is expected to be achievable among the diversity of perspectives protected by religious freedom/liberty. In the case of moral liberty, on the other hand, it is expected that in the absence of state religion and abuse of authoritarian power, religious freedom results in people taking the liberty to arrive at common standards of decency in governance.
As for Relativism, I think there is some truth to it, people are basing their morality, for instance, of ideas they adopt influenced by society and other outside sources in relation to themselves, which tend to treat themselves and others well. That's all morals are to me, to me they are not typically some absolute set of rules to be demanded universally. I'm pretty sure if we looked at morality closely enough we would find paradoxes and exceptions to the Rule
Relativism cannot negatively evaluate rationalizations and whitewashing as morally wrong/bad. They are seen as one perspective/prerogative among others deserving of equal validation. Relativism ultimately cannot distinguish between lies and honesty, for example, because the prerogative to lie and cheat can be validated by relativism as a religious prerogative equal to any other, e.g. Satanism.
As for God, he isn't our understood version of Man. And I think neither is reality; God's understood view of reality is not that close to our understood view of reality. We see the physical universe and not much else, I would include energy to that physical universe. With God I tend to see that God promises another universe instead of this one. He also promises to remove all corrupted elements before that new universe is manifested. That is why I tend to think that we are not looking at the perfect anything in our universe. It all has an expiration date. Nothing is permanent. Our universe is temporary and an exception instead of the rule of eternity.
The universe consists of energy and all its manifestations and transformations. It is simultaneously perfect and imperfect as it contains all potentialities and forms. In the Lord's Prayer it says, "Thy will be done on Earth as it is in Heaven." The implication is that we aspire to facilitate God's will in our world to the best of our ability despite the fundamental imperfection built into nature.
Nothing material is permanent, because of the fundamental nature of energy as motion and transformation of form. However, there is a spiritual level that transcends materiality in which eternal life is axiomatic. E.g. if you understand energy in terms of the law of conservation where it can neither be created nor destroyed, then you automatically understand that one form transforms into another without ever stopping due to 'death.' In other words, death is an illusion caused by focusing on material form as an isolated state of existence. Once you see material form as a temporary configuration of something that is permanent, death is no longer a finality.
I hold those views, and I don't expect anyone to adopt them just because I hold them.
While it may be unrealistic to expect any person with a free mind to adopt anything in submission to reason, however reasonable it might be to do so; you should also have no reason to validate the rejection of reasonable beliefs by people as an assertion of absolute sovereignty/autonomy of arbitrary prerogative over reason.