To dress really casual (unless the wedding is a beach wedding or the invitation states that it is casual or themed such as western wear) shows disrespect to the bride IMO.
Part of being an adult is accepting that certain occasions call for certain behaviour and we may need to bite the bullet and act (dress) accordingly. But that's just me and I tend to want to do the "proper" thing.
As for the groom not wanting to be there, it sounds as though this marriage is starting out on the wrong track and may be doomed to fail which is unfortunate.
Part of being an adult is accepting that certain occasions call for certain behaviour and we may need to bite the bullet and act (dress) accordingly. But that's just me and I tend to want to do the "proper" thing.
As for the groom not wanting to be there, it sounds as though this marriage is starting out on the wrong track and may be doomed to fail which is unfortunate.
