discourtesy vs subject matter

discourtesy and subject matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
discourtesy	Yes	No	No	No
subject matter	Yes	No	No	No

As nouns, subject matter is a hypernym of discourtesy; that is, subject matter is a word with a broader meaning than discourtesy:

Other hypernyms of discourtesy include content, message, substance.

discourtesy (noun)	subject matter (noun)
a lack of politeness; a failure to show regard for others; wounding the feelings of others	content communicating a message; what something is about
a manner that is rude and insulting
an expression of lack of respect