It is because I feel a deep and tender interest in your present and eternal welfare that I am willing thus publicly to address you.
Angelina Grimke definitely felt passionate on how she felt about slavery. She was often criticized about it and separated her idealistically from even your family. This is like the warning to the topic, it may be sensitive and you can tell it a touchy topic because she is trying to illustrate the uncomforting that she is facing that is in the hand of all her sisters (Women, often white women).