When a kid in school acts in defense against a school bully, why do principals/teachers often go for the victim, instead of the bully?

This is a tough one honestly. Maybe not all places have teachers that do that but a lot of them certainly do, not sure if there is anything that can be done. Bullying is inevitable though so I'm not really anti bully in the way a lot of other people are. I remember seeing this bully victim on tv with his parents explaining how much of a problem it is and the whole time I kept thinking the parents are the ones creating this situation. If your taught to think that your a victim, then that's all you'll ever be.

I could NOT agree with you more, its probably because they don't want the parents of the bully looking upon them like they advocate violence.

I think that's complete BS and I've had personal experience in this matter, they told me to walk away even though I couldn't and give me a detention, they're more worried about defending their image than they are you getting injured and that's the truth.

PS, if your teacher or your parents have told you if someone bullies ignore them, don't, punch them in the face. Bullies understand violence and they won't do it again, they don't understand a teacher shouting "I AM VERY CROSS WITH YOU!" and the teacher does it not because they give a toss, but because they have to.

Maybe it's easier to treat the symptoms rather than the root of the problem itself.