I can not treat thjs question but with the spice of humour as in my post above , relating to the latter day Faithful& Discreet Slave. To come to a good turn of events, You would have to ask preliminary questions like: Did not all Christians partake of the emblem since The First Memorial? (ignore the fact that the first partakers were not Christian=anointed); then ask:- so when did the Other sheep christians start abstaining? so,-- then since that convention, there were two classes of Christians? OH, so the Other sheep Great Crowd members are not Christians? so, you are saying that almost all partakers before 1919 will not be in heaven but resurrected on Earth? Can you see how not partaking is a mistake, because of that, you will have to work 1000 years in slavery to reach the same status that partaking affords "true Christians" right away?
Perhaps you can get them to laugh along with you at the answers and that will take the edge off the confrontation.
or keep going: Since to get everlasting life, you have to partake (John 6.) , will the Great Crowd start partaking after they come out of the great tribulation? going back to the Last Supper situation where the Earthly Class guests Partook?