That defeats the purpose of having Sacrifice in the first place.
I want it to be available to use Military Units/Capital Ships to generate "Propaganda Broadcasts" to sacrifice and generate culture by winning battles. This allows you to generate Culture via military action, such as having a civ which do not generate much culture from improvements at all, and their only recourse is killing units, and thus opening an entirely new style of play.
However, if the AI cheats and sacrifices worker units that are not intended to be sacrificed, that's a price I am willing to pay if the workers are low cost, as the AI is generally incompetent anyways. If they are high cost (say, 50 shields), 2 workers is suddenly enough to expand the border twice. And I've seen the AI capture much more than 2 workers at a time in some test games I've watched. It gets a bit much when a well developed city is captured, and suddenly has double the culture as it originally had, just because the AI sacrificed the 4 workers that captured along with the city.