I don't think it's unreasonable for people to think that a Christian wedding is in some sense more real than registry office weddings. In the sense that a marriage is a commitment between two people then they should be considered equal, but in the sense that it is also a commitment before God then they are not equal

Yeah, but, I don't think that is what they're doing. It's not "church weddings are right because they have God TM, and registry office weddings don't", it's a much fuzzier set of ideas about why church weddings are right. And so they pick a church wedding because of those fuzzy reasons, and then get annoyed that it comes with so much God TM.