My mil was not happy when we told her about our planned pregnancy (we were married, good jobs, stable etc etc). I found it very hurtful and it put a dampener on the rest of the pregnancy.
When you're pregnant and excited, it feels so personal when other people see your baby in anything other than the positive light that you do. I really do understand that. I also get that sad sense of not being in control and have given certain things that you hold dear, away. At the time, it can feel like the experience has been tarnished. It's not reasonable, nor actually important in reality, but it can sting so, so much at the time.
I imagine that your husband feels upset and embarrassed and he was just desperate to generate a little positivity from his family. It must have really hurt for his own family to disregard his own baby like this. I know my own husband was very hurt and upset with his mother and made her apologise to me for her initial (horrible) reaction. She was actually very remorseful and cried when she said sorry. That baby is now 5 and a delight in all of our lives. I know mil feels mortified to this day.
You will have a lifetime of beautiful and special moments with your baby, many 'firsts' (for you both) and nothing will compare to getting to know your son. Without getting too sentimental, holding, smelling, looking at, squeezing and kissing that little human will put everything into perspective perspective the time arrives. As you watch him grow, develop, reach his milestones and become his own person, this will be a distant memory, for everyone! Just wait!