we have a different set of expectations for in-groups than we do for out-groups.
We expect our in-group to act like us, and blame the out-group because they are not like us. This hits home hard. Despite everyone saying they are not biased, everyone has some sort of bias in their life, and they unconsciously set certain expectations on our in-group because we expect them to be like us and act like us. Our expectations for our out-group are often associated with bad things, them messing up in some way, or that they will not be "as good as us."