So, given that an AI civ has established a Religion. It has established all its cities to that Religion. Then another civ comes in and converts one of those cities to its Religion. The city-owner now has one of its cities NOT adhering to the State Religion. Then the human player comes along and converts that city to his Religion, from the third-party Religion it had previously been converted to. Under the above situation, why should the city-owner get full grievances for the player having converted its city from that third-party Religion? It is pointedly different from the situation where another civ is converting the city from the State Religion. Regardless, it will take the city-owner's sending in Missionaries and Apostles to convert the city to the State Religion regardless if the city had no dominant Religion, or was dominated by another AI civ's Religion or if it had subsequently been converted to the player's State Religion. It isn't like the player "stole" the city from the AI civ. It had already been "stolen" by a different AI civ.