I have heard Catholics distinguish between themselves and 'Christians'.
It may not be 'official' RCC doctrine.
As for coming up with Vatican Documents, the Vatican has a document to take any side on any issue.
This quote from you...
you also said "That is not the Roman Catholic Church which is a particular denomination and even many of them do not call themselves Christians."
I did not write this! You wrote this!
I pray this is just a mistake on your part but,nothing would surprise me coming from anti Catholics such as yourself!