In order to have those you have to prove subjective morality exists which you can’t.
Not at all.
Firstly linguistically speaking no moral standard can be objective so what you are arguing is that morality doesn't exist at all.
If morality doesn't exist I can still have opinions about morality in the same way I can have opinions about anything else fictional. I can have opinions about Odyseus for example or about the magic in harry potter.
In fact even if there were some objective moral standard (which you have not demonstrated) well I can have opinions about objective things too. Earth objectively speaking has gravity. I am of the opinion that the gravity on earth is just right.
Do you not see how your argument is self defeating?
If you see a problem with my reasoning please point out the SPECIFIC flaw or offer a LOGICALLY NECESSARY counter factual.
Or if all this seems like a little much maybe we could talk about the basics as I've repeatedly offered.