Here is an interesting article about research on sleep deprivation. The researcher did three studies, where she sleep deprived students and assessed their prejudice and stereotyping of others. Her results suggest that sleep deprivation may negatively impact people's expression of prejudice and stereotypes. It's not clear how sleep deprived the students were during the experiment - was it a total night of sleep loss, or chronic partial sleep loss?
In the article, the researcher is quoted saying, "In our research, we found that sleep functions as a self-regulatory resource that, when depleted, leaves people less able to control their thoughts, attitudes and behaviors in a non-prejudicial manner." And, she is quoted saying, "By having a good night's sleep and being well-rested, individuals are more likely to be able to act appropriately in situations."
Of course, being sleep deprived is no excuse for behaving inappropriately, no matter how tired we may be.