Would you like your DP (say) to receive an intimate examination by a doctor with her boobs hanging out of her top? Or your child to be taught by a teacher in a "mankini"?
If we're discussing appropriate conduct by professionals in a position of authority and trust - which a bride is not - then I'd class it alongside a minister talking about a member of the flock, based solely on her dress choice no less, with the phrase, "slack fannied trollop". And at least those people aren't in the habit of claiming greater moral authority as the sole foundation of their role.
See, this is the thing: the church is meant to be a place people go to have a relationship with God. It's not a professional setting. It's a place people go to seek spiritual solace and fellowship. Some will take advantage of the setting, but that's an opportunity for outreach - it's not meant to be an exclusive club, is it. And as soon as you start saying or even thinking that certain sorts of people are good and classy enough and others aren't, then by definition you are being unChristian. Lepers had their feet washed by Christ. He defended a woman taken in adultery. So a gleeful, sniggering mockery of someone who is, "classless" "common as muck" "had her tits out" because she wore a dress a few sizes too small on her wedding day, and then saying the outrage is because she was in a Church and it's awfully important to respect Christian values... well, speaking that way about someone, laughing at them and denigrating them as comprehensively and contemptuously as has been done here isn't respecting any Christian values I recognise. It's incredibly ironic, actually.
It's completely reasonable to talk to a bride before the big day and explain that you would like a dress code of X Y or Z if that matters to you. That's fine. Cultural traditions are important, and indications of respect within a culture are of value. That's very, very different to a bunch of people gleefully competing to see who can be the most spiteful about a bride, and who can make the most vindictive remarks.
It's really sad that it's necessary to explain this to a member of the clergy. Again, I think some spiritual direction is necessary because this isn't walking in the Light.