Justifiable % defence is the act being exempted from crimes, namely, this act appears to cause damage to lawful rights and interests, but in essential it protects lawful rights and interests.

正当防卫是排除犯罪性的行为，也就是说，这种行为在表面上给合法权益造成了损害，实质上却是保护了合法权益。

youdao

Robert and I are collaborating on a book about the next generation of online technology and he has a stake on my not doing anything stupid in public related to social technologies, so the appearance of my spamming hundreds of people on Facebook was a justifiable cause for his concern.

FORBES: How Did I get Hacked and Why Didn't Facebook Help?