Your boyfriend is stubborn and if he continues to put “his principles” ahead of his relationship with you, he’s going to wind up lonely. When you’re with someone who doesn’t compromise you can either agree to his way of doing things or you can leave.
The middle ground, however, is the best solution. See if he’s interested in this: compromise.
If you can both agree to disagree on issues, then the only problem is equalizing the number of wins you have and the number of wins he has. If he wins every single argument, then there’s not much space in the relationship for you. However, if he is willing to give you half of the wins even though he understands that they’re against his principles, but he’s going to give you the win because he loves you, you can both make this work.
In any long term relationship, no couple will agree all the time. Especially the longer the relationship exists. What keeps relationships together is compromise. This is a dynamic that children learn on the playground — under the guise of sharing. It comes harder to some people than others, but basically, it’s a way for people with different needs to coexist.
See if your boyfriend is willing to share and compromise. If not, you’ve got a losing relationship on your hands.