I wouldn’t use that terminology personally, but I would say a universal moral standard is non-existent yes. That presupposes a situation where in two locales one can find identical histories, cultures, individual perceptions of cultures etc which simply in practice cannot happen.
What I would add on to that however is that there are morals which are more likely to be shared by cultures. Take for instance state sanctioned execution of the disabled or mentally feeble. We know there are societies in history, modern and ancient, such as Sparta and Nazi Germany who found this to be a moral good. In these societies physical strength and military power were seen to be the chief value in many respects, so actions towards furthering this value (purging the state of individuals who did not contribute towards it) was a “good”.
The vast majority of tribes, cultures, states etc have not; particularly in the more recent centuries with the occasional exception have not seen this as a moral good, because such an action conflicts with whatever their chief value is; freedom, filial peity, arete/honor. There’s a wide variety of them with which that would conflict and again leading to a majority seeking to punish or purge the individual/group which disagrees with their moral code. Oddly enough, the Catholic Church on gay marriage is actually a fantastic example of this; it’s not enough for a Catholic to not contract a gay marriage themselves because they dislike it: they are compelled to prevent everyone else from obtaining one as well because they find it so awful. Muslims on pagan worship, the North Korean government on South Korean media; it works for so many contexts and cultures.
Theft, cannibalism, incest, rape etc. These things tend to be near-universally condemned, with exceptions like IS, because it is near impossible for a stable state to be formed when one is at risk of being eaten on the commute to work or it becomes impossible to breed reliably due to severe genetic malfunctions
TL;DR: There’s no such thing as a universal moral code, but there are specific taboos such as a prohibition of theft which are more likely to be shared and condemned by relativistic codes than others.