I definitely believe this is a deal breaker and I agree with both sides here.
He has his views on marriage and you have yours. You both have different needs and desires in life and if a partner cannot reach them, then I believe they shouldn't be together. Same as with children. These issues, to me, cannot be negotiated unless one person gives in and that can sometimes create a life of resentment in one partner.
If you need marriage, then I think you should have marriage. And if he cannot give it to you for whatever reason, then I understand you're walking away and I surely wouldn't think you were wrong for it. Your reasons and feelings are valid just as his are. If you both cannot compromise, then it can't work.
I never wanted marriage. I guess you can say I was the type of person who could either take it or leave it. In my mind, I thought more like your boyfriend. It mattered more to me how a person treated me. My husband on the other hand, felt exactly as you do. Marriage was a priority for him and I understood where he was coming from.
Eventually after dating, living together and being engaged for 3 years, we married. I was happy to give him that. His happiness made me happy in return. And I knew that even if we weren't married, the commitment would be the same and I was in it for the long run. We've been married for a little more than a year now.
Marriage has not changed our commitment and it hasn't ruined us. We are even stronger today than we were back 3 years ago. I wouldn't change anything. I am happy and I'm glad that I decided to marry my husband. But then, this is my experience. I know not everyone will feel as I do.
I hope you both can work things out. But I also hope you both don't force each other into something you both aren't willing to give. Best of luck to you both.