But Britain is the parent country, say some. Then the more shame upon her conduct. Even brutes do not devour their young, nor savages make war upon their families. What does that mean

It means that the behavior of Britain wild (savage- like) which was describe that only an untamed animal will wage a war on his families.

Explanation:

This is the principle of common sense where  mother -country  demand the right to obedience from the child which was used to describe how Britain behavior did not portray her as a mother country to the child like they are families or allies, hence the child needed protection from her untamed or wild attitude.

The above excerpt is related to Thomas pain argument that the  13 colonies who believe they do not need the support of Britain to advance the growth of their colonies.

answerhand and arm extended upward;