Because of the imprecision of your definition and because you won't deal with the theological or ecclesiological considerations which define "Catholic", are you saying that FR forbids, unless expressly invited, Orthodox Christians from posting on any thread designated "Catholic Caucus"?
The above ping list is the "Orthodox list" and does include a number of Latins and always has, on purpose!
The Orthodox have been invited guests in the Catholic Caucus all along. And everything was going swimmingly until a critical remark ("uncanonical behavior we Orthoox have come to expect from Roman Catholic hierarchs") made and endorsed on the caucus resulted in an abuse report and this confrontation.
In the future, a caucus guest should ask himself if what he wants to say is something he would stand up and say in the midst of a closed door church service. If not, then it is inappropriate for that time and place - save it for an "open" thread.
I imagine Catholic Caucus posters will again extend their welcome, but if the guests cause a disruption, the posts will be pulled and they will be instructed to leave.