It seems to me that argument is a bit circular. If one holds to the theistic belief in a creator who also imbued creation with a foundation in morality then it is not merely a matter of personal taste. The response will be, of course, that believing that is a matter of personal taste. Yes, but it either it is true or it is not. Personal preferences are not founded in something objective. Either there is a moral foundation to the cosmos/creation or there is not. We can have different opinions on that but ultimately one will be right and the other wrong.