DEAR MISS MANNERS: Because of COVID, we had not been having our regular family and friends Seder. We were happy to restart the occasion and had a rather large gathering. During the Seder, one of the family began an online call at the table with a missing relative who was invited but declined, as they lived out of state. This call lasted 10 to 15 minutes, in the middle of the Seder. I considered beating the caller with a stick, or at least dousing them with wine. My spouse was similarly angry. This guest is, at best, unpleasant to be around. This night, they exceeded unpleasantness and selfishn…