"most utilitarians think that sometimes people are not to blame for performing actions that are very wrong, and that sometimes people should not be praised for doing the right thing. why do they think this?

 The correct answer is :  Utilitarianists make the correction of an action dependent on all its results, regardless of the time that has elapsed after the action. There is no statute of limitations to count the consequences. This causes inconvenience since the action of someone can lead to something bad, but the person could have intended to do something good and did not get a good result, but it could also be someone who from the beginning had bad intentions. People who have bad intentions should be blamed for their actions. Individuals should be commended for doing the right thing, but if they had bad intentions and in the end something good was reached, in this case they should not be praised. Utilitarians should rely more on intentions than actions.

it is a bolivia your welcome