Many people instinctually defend or stick up for a family member or loved one when some sort of feud arises or a disagreement occurs. This is not necessarily a "toxic" trait to have, per se, because it most certainly illustrates your loyalty and affection for that person. However, it's important to remember that just because a person you care for is in the midst of drama, it doesn't always mean you should be defending that person.
If I say something offensive, tell me. Pull me aside and explain to me whatever I said is wrong and knock some sense in me. THAT is what someone who cares about me should be doing — not justifying my wrongful ways.
I always try to do this for others as well. I will always apologize on someone's behalf if my loved one behaves out of line and consult said person after the fact. I will not simply defend you because you are "blood" or because we are "best friends." In fact, I will NOT defend you for that reason.
This is not to say you should throw your loved one under the bus. By no means am I saying you should ever degrade anyone for what they're saying or doing. Rather, there are many ways you can maturely address the situation by acknowledging your loved one is in the wrong. This allows the situation to heal properly and nourishes the self.
Understand that you are not being a bad child, parent, relative, or friend if you are not quick to defend someone because you recognize the red flags. If you didn't already know, we are not all perfect! We all say and do things we don't mean that get blown out of proportion, and that is OK. It's part of life. But, we need to recognize when we are wrong and when others do wrong in order to make everything better.
It may not seem like the natural or ideal thing to do in the moment, but having a grasp of morality and a sensible mindset always triumphs the negative repercussions that will come as a result of defending a misaligned individual.