Am I overreacting?

My SO and I decided that we would not reveal our baby’s name to anyone until birth. We made this decision based on negative responses and opinions we received when we were discussing different name options. I told my SO that reading those comments hurt my feelings and I did not like the feeling of having our child picked on before he was even here. I was told today by his eldest child from a previous marriage that he told his ex-wife (whom I don’t have much respect or like for, based on other circumstances) behind my back. I told him that I was hurt and felt disrespected that he did not honor my wishes, as I was wanting this to be a special and intimate moment for us and our blended family together, as this is our first child together. Now, I am the bad guy and am receiving the silent treatment for tactfully explaining how I felt and that I did not appreciate him telling anyone the name without speaking to me. Am I overreacting or am I justified?