I've seen many things described as a marriage. Like special diplomatic relations between countries, business mergers, even product announcements. And I think that people can understand this. Once again, try to describe civil partnerships to somebody. What are you going to do? Say 'It's like a marriage, just don't call it so, because I don't like it'

(In the same way, I'd even describe your reason as 'religious, just there are no gods and churches and other deities involved'. We are also used to call fanboy disputes between the text editors or operating systems as religious wars. And it's a very good description.)