Principal told my son "Be happy she had that miscarriage"

Me and my son have been fighting so much lately. I had a miscarriage a few weeks back at 15 weeks. I had to get a D/C and it was extremely traumatic. My son is adopted and I thought I would never get pregnant. I've been really emotional and he's a teenager so he pushed my buttons. He got sent to the office yesterday for not listening and was talking to the principal. He was complaining about me and he told my son "Just be happy she had that miscarriage." My son told me about it and I went and spoke to the principal and he said "Well I just meant it as the baby would have probably complicated things since I know you as a family are going through things and it's a good thing you don't have that extra thing added on top"

He sees nothing wrong with telling a 9th grade boy to be happy his mom had a miscarriage. There are so many things he could have said. Am I overreacting to this? I feel he did not need to say that!