disgust as a noun or verb is a powerful word. Its meaning has become more precise and distinct over time because research has been done on the emotion of disgust over the last several decades.
This Wikipedia article defines disgust and describes some of the research theories and findings:
Disgust is an emotional response of revulsion to something considered
offensive, distasteful, or unpleasant. . . . Disgust is one of the
basic emotions of Robert Plutchik's theory of emotions and has been
studied extensively by Paul Rozin. It invokes a characteristic facial
expression, one of Paul Ekman's six universal facial expressions of
emotion. Unlike the emotions of fear, anger, and sadness, disgust is
associated with a decrease in heart rate.
The article also notes:
Disgust is one of the basic emotions recognizable across multiple
cultures and is a response to something revolting typically involving
taste or sight. Though different cultures find different things
disgusting, the reaction to the grotesque things remains the same
throughout each culture; people and their emotional reactions in the
realm of disgust remain the same.
These findings suggest that the meaning and use of the words are not simply diverging in different parts of the the globe, but have the same meaning and nuance everywhere. Therefore to call someone disgusting is, if the word is properly understood, an insult and rude, as you suggest--not a joke--no matter where you live.