Ok My Eve Sisters, I need advice

My husband and I have been married for almost 7 years and he has a 6yr old son from a previous relationship. He told me that it was just a one night stand, and I don't care because what happened b4 I met him does not concern me. Anyway, the youngster and I get along well. I really love him. His mother went on my FB page and saw a picture of him and his father that was originally on his fathers page, and I shared it. She sent me a message saying that she did not want her child's pic posted by anyone who is not family. Sadly, I thought that there was nothing wrong with me posting this pic because in my heart me and my stepson are family. Was I wrong? Was the mother just upset because I married her son's father years ago, and she still can't deal with it? My husband told me to block her so that I don't have to deal with her foolishness. He also told her, to keep my name out of her mouth and grow up because she will never have his last name. It's been 7years and I am wondering if the drama will ever end. Help me!!