We have to excercise our choice whether or not we are delighted about the other options. We cannot let any party get too entrenched or feel too safe.

If the message "I suppose I'd rather eat cat shit than dog shit" is then interpreted as "I really love cat shit, feed me more" I'm not sure that works.

It's more like crop rotation than a message. If you grow the same crop in a field too often then it impoverishes the soil and allows pests and diseases to build up.