YANBU, it's typical bullying, expecting you to subjugate to peer pressure on such a principle. Absolutely normal disregard of non religious views and revealing that, frankly, Christians often do not practise the values they preach.
Instead, I would hope that in future they check their behaviour, give you space in an often suffocating world to not be co opted. It's not like you went out of your way to blaspheme or call them on their collective, erm, fantasy.
Sadly you can't win I suspect, if you are as servile as some expect you to be, to satisfy their arrogance it will get worse, you will have no voice. If you stand up for yourself even with constructive disengagement you'll be seen as awkward but at least you have a voice.
As for your husband. Words fail me, he doesn't have your back and doesn't respect your attempt to draw a reasonable line. In short, he owes you a big fat apology. He chose to marry someone outside his faith, if he wasn't prepared to compromise on this, and can't act as a peacemaker then he's not going to have your back full stop.
I'd hate to be in a relationship that isn't equal or based on mutual respect, and I don't envy the work you have cut out for you.
Ti's the season for the veneer of Christian tolerance to wear thin, tralalala... la la la laaaaah.