Because "their" rights and "our" rights (whoever "us" and "them" happen to be) are one and the same. You wouldn't be defending or attacking "their" rights, you'

Because "their" rights and "our" rights (whoever "us" and "them" happen to be) are one and the same. You wouldn't be defending or attacking "their" rights, you'd be defending or attacking rights in general, and that includes yours.