Religious differences?

My boyfriend and I are different religions (Im Roman Catholic and he considers himself Jehovah's Witness even though hes not baptized) and everything was going fine until he mentioned something his mother said. He said that his mother told him to consider getting a new girlfriend from their congregation/church. This didnt hurt me as much as it bothered me. He told me hes okay with our religious differences, but im not sure I am after what his mom told him. Should I just let it go? Am I just making a big deal about it? Advice is greatly appreciated :)