One of the key markers of rationalization I've seen is rationalizations ignore tradeoffs and other option. This is obviously true only about the rationalizations about actions and policies. For instance "I want to eat the whole cake to help the sugar industry..." never finishes "...and this help to the sugar industry is worth any ill health effects." or "...and this is more efficient than other ways to help the sugar industry,"

One activity that might help is to give people a plausible proposition to argue for in their own life that they do not follow. So "Veganism is the optimal dietary option." could be given to someone who eats meat. Have them argue for it, telling them that they will only be evaluated on the persuasiveness of the argument. After this is done, ask them what costs and tradeoffs are for that position. Also ask them what other alternatives there are to achieve the goals and values they hoped to achieve.

This can provide an example to the participants of what rationalization and the results of rationalization looks like. It also provides a demonstration of the efficacy of a couple of questions to catch rationalization.