Only the people involved can answer this question.
What's important to one person may not mean much to another person.
Generally speaking however I would say anytime you have to give up something that keeps you from being true to yourself then you have crossed a line. Your (core principles) are what make YOU who you are.
Ultimately each of us wants to find someone who will love, appreciate, and adore us for who we are.
If you have to give up your core being to be with someone than you need to move on.
It's not as though they are wrong for wanting what they want. It's just that they are wrong for you. In fact I'd take it a step further.
It's not about Right or Wrong but rather Agree or Disagree. If you don't agree on the major things then it's time to move on. Thankfully there are over 6 Billion people on the planet. One has to like the odds that there is more than one person who wants what you want!