Toxic Shock Syndrome

I know that it is an actual disease, but I'm adopting the term to mean something else. For me, toxic shock syndrome (TSS) occurs when someone that you love and trust (i.e. your mother, grandparent, sibling says something so hurtful, mean and toxic that it sends you into a shock like status. Normally, if anyone else were to say something along the same lines, it would be the end of a friendship and most garner a bitchy response, but since the comment came from a loved one, all you can do is stare at them with a blank look on your face.
Why do people think that being related means that you can say toxic things? It isn't love that says those things. It really bothers me that people do this in the name of love. When loved ones say toxic things, sometimes, all I can think of later was that comment, and how I would have responded to it had it come from anyone else but I bite my tongue because I don't want to hurt or alienate anyone.
One example of TSS, would be the time that my grandmother looked me dead in the eye and simply said "You're getting fat." She's not overly old and there is nothing affecting her mind, but she felt the need to tell me this. I wanted to snap something back, or just leave, instead all I could do was look at her in shock and when I regained my composure a bit, I changed the subject.
My mother is the queen of TSSS (that's toxic shock syndrome statments). The other day, she came into my home to pick up my brother, who had stayed here for a few days. In the course of converstation, she said to me, "Ugh, your house is getting as bad as Amanda's." Now, I need to explain, my cousin Amanda who I loved dearly was not the best housekeeper, in fact she could have gone on that show "How Clean Is Your House?" easily. Her house was disgusting, I think it was the only house that I have ever been in where I did not take off my shoes. Now, I was always polite to Amanda and I would never think to tell her that I found her house repulsive, but this is just to give you an idea on how big an insult this was. Now again, I will admit, I'm not the best housekeeper, with the two rugrats running around, I just try to keep up with the clutter as best I can, but it is seriously not too bad. When I have company over it only takes about an hour to hour and a half to get everything in order and that usually includes washing the floors. If it's just friends who only merit a straightening, it takes about 20 min. I mean frankly, I probably clean more often then she does, given that I have to vaccum like 2-3 times a week. It was just really hurtful and painful to have her tell me that.
Sorry all, I just needed to vent.

(P.S. I think I'm going to keep this background!)