Rationality is the basis which choice relies on, without rationality any choice would instead be a random result rather than considered.
In most cases people are able to evaluate which course would be better for them, if you offered a sane person the choice between having a muffin or a finger chopped off, it should be clear to the reader which option will be taken.
People will always opt to take a choice that suits their needs and goals and morality, over ones that suit other peoples.
It is important to say that a parent making sure that their child is eats before they eat is acting in their self interest as their goal is to make sure that their offspring survive.
They confuse several things
Critics cannot say people in general are irrational, their motivation for this is most likely that they would like to remove the responsibility of choice from these people and control their actions.
If people in general were irrational, how would society have achieved the level of organisation that we see in our daily lives and where did the microchip come from? Was the microchip developed in an irrational environment? Beleiving that would be irrational!