Okay, Twiffer - a post to try to answer your question.
There are at least two very important senses of the word “morality” for the philosopher. One sense is this - personal rules for living. In this sense, philosophy can be seen as only morality. “This is what I know, and this is what I don’t know - so how shall I live best?” sums up philosophy understood as an activity - as what a given philosopher does qua philosopher.
The other sense is as one of several fields of study within the discipline of philosophy - the study of known and putative moral systems. For a perspectivist (at least), the latter is often informed by the former.
For context, the main philosophical influences on my view are, as I have stated many times, Hume, Nietzsche, Russell and Ayer. It is true that I left some questions unanswered in the thread about Evolution and Morality, but that is because my vocabulary is very different from Cyrene’s. I was struggling to use a style of expression that I am not comfortable with. This mainly because I was seeking the common ground between Cyrene’s and my positions. I didn’t want to stray too far from that task.
One or two of my basic assumptions are quite obvious - I am an atheist and a materialist. And a perspectivist.
Materialism is, of course, entirely consistent with Cyrene’s view. I simply draw a distinction that was not evident (to me) in Cyrene’s recurring thesis - the distinction between physical responses (including what we refer to as emotional responses) and moral judgements. The analogy I would draw is this - one can walk around a meadow and get a sense of its size, and one can measure it - mathematically. Moral grammar is, by this analogy, the ability to understand measurement. Morality is the measurement itself - and like all mathematics, is not real. It’s an abstraction, made possible by an innate ability. And like mathematics, I don’t have to have invented it myself in order to understand it when it is presented to me. And our physical responses, or processes, are like walking around and actually experiencing the object of our moral thinking. But not every walk in a field is necessarily a candidate for moral thinking - the ones we choose are. Or that are chosen for us.
As a materialist/atheist, I must of course rule out any unreal inspiration for moral thinking, but I am not required to allow that morality cannot itself be unreal. It can be as unreal as such useful conventions as God or mathematics. By “aesthetics” I mean personal tastes, even very commonly found ones - yes, like taste in who to have sex with. I do not see homosexuality as a moral issue, and I would not easily accept that any evolutionary psychologist would. What I see as moral is the (unreal) measurement of that taste. Yes - emotional, visceral, unmeasured reactions to homosexuality are real - as Cyrene has pointed out - they are brain activity, that can be observed. But morality is only claims about those brain activities - and in that way exist only in language.
Morality can only belong to philosophy, for morality exists only in language.
With me so far?