I've REPEATEDLY asked for a term for Roman Catholics that I could use in good conscience that would be acceptable to them.
THEY HAVE ALWAYS FAILED TO COMPLY.
Therefore, their wailing is disingenuous, to the max.
I note that the official Vatica site, Vatican.Va , refers to itself as "Roman Catholic" hundreds of times so it would be difficult for me to imagine someone taking umbrage at the abbreviation RC or RCC.
No matter, I will continue to use it without apology.
As an aside, I have seen frequent references from RC's of FR to a quote from Augustine; "Rome has spoken...", also from Ignatius; "Rome has spoken..." (Whether spurious or not is not the question). I would imagine that is implied permission for you to use "Rome" as a substitute for "Catholic" as you wish. :-)