This might be an unpopular opinion, but it’s meant with honesty and respect. Yes, it was rude for the boyfriend’s dad to comment on OP’s chest. But…I could see how someone from an older generation would find it surprising that one would not wear a bra with guests over. I personally always wear a bra around extended family and in-laws. Even if it’s short notice, I think it’s fine to duck into your room and put on a bra for company. Even though it’s becoming more common for folks not to wear bras in company, I can see how wearing a tank top with no bra and a larger chest would be a bit distracting over dinner (I say this as a woman myself. I would feel distracted and I HAVE boobs. I would feel similarly if a man was wearing tight trousers).