Yes, the "quit what you love or i'm quitting you" seems like a pretty dumb way to start any relationship. And admittedly is sadly common.
Something tells me this is more of the "what is this new obsession and how does it fit into our life" situation that comes up on here all the time. New couples should be very aware of what makes each other tick and be supportive. On the other hand, if you take up a new, completely consuming (i.e. boat restore), and expensive hobby then it is up to YOU to do all you can to gently and considerately blend it into the relationship. You can really blindside your significant other if you wake up one day and tell them you are a sailor. Kicking your SO to the curb because they don't immediately get in line with your new obsession is damn extreme and frankly odd advise to give someone you don't know on a forum.
totally agree with this and please understand I was not recommending my method for anyone else. cycling has been part of my life since I was 4, not optional to give it up.