I would presume that symmetry would be boring, that a lack of it would be more interesting?

Beauty depends on culture. However, some things that are abnormal or detrimental such as acne, moles, etc. are usually undesirable regardless of culture.

It seems to me that there are two different questions being treated as one question.

1. Is there, in fact, some universal standard which is accepted.
2. Is there a correct universal standard whether it is accepted or not.

Those are not the same question. It does not follow that because some standard is accepted that it ought to be accepted. And it might be that although different standards are accepted in different cultures, that some are closer than others to the correct standard.

You cannot just assume that beauty is relative from the get-go.

It's not from the get-go. It's seeing that there is variance in what people define as beauty. If not everyone agrees then it must be relative, right?

No. Not everyone agrees on whether there is life on other planets. Is that relative? Or whether there is a God. Is that relative?

You cannot just assume that beauty is relative from the get-go.

If we're speaking of beliefs, then yes. If we're speaking of facts, then no.
But can beauty be a fact?
Is beauty not simply how pleasurable something is to one's sense of sight?
Or something else?
What are you defining beauty as?

Why not, if the idea of 'beauty' clearly varies from person to person, culture to culture, time period to time period, etc? That there is some absolute measure of 'beauty' is a claim that needs to be proven, because relative beauty that exists 'in the eye of the beholder' is quite apparent.

In western culture, for example, 150 years ago, women were seen to be more 'beautiful' if they were somewhat plump (well-fed but not fat) and pale in skin tone. Now, what is 'beautiful' for a woman in our culture is to be tanned and skinny. Of course there are a host of other things involved when determining if another person is 'beautiful' or attractive or not, including evolved psychological responses, facial expressions, tone of voice, social status etc...

It's also interesting that we talk of 'beauty' when referring to pleasurable sights and sounds, such as a painting or musical performance. But the other senses somehow do not convey 'beauty'...people typically do not say that a touch, smell, or taste is beautiful. What is it about sights and sounds that can be beautiful? Is beauty even something that can be logically determined, or do we just 'sense' beauty immediately when it hits us...because in my experience, it is the latter.