All I can say is that when two are in a relationship then quite simply both partners should be willing to listen to their other half.
Whether you each agree with each other's point of view is irrelevant but more importantly if you disagree then you agree to disagree in a respectful way.
Once you've both aired your own thoughts and discussed them then hopefully you can compromise and find some common ground between you.
Sometimes you might not be willing to give up some ground because you hold a strong belief or principle - That's your right and you should be able to justify that if you're not willing to concede any ground on any issue which is personal to you.
You say that you feel betrayed when he tells you the truth and that you feel he's not on your side. You should respect the fact that he is being honest and try to put yourself in his shoes. Can he justify his honest thoughts? That's the question you have to honestly ask yourself. It's not easy to be impartial when you're emotionally involved. Can you stand back from your own emotions and rationalise whether your boyfriend's honest thoughts are justified? If you can then you can reason whether his thoughts are justified.
If he is right then you have to be understanding and try to accept his point of view. Women, as you know are creatures of emotion, so women can take things more personally and will be more sensitive to any criticism especially when it comes from the one they love. That's where you least expect it to come from so naturally it is going to hurt even more than say some criticism from Joe Bloggs who means nothing to you.
So listen to him carefully and try to put yourself in his shoes, and try not to feel that he is betraying you with his honesty. But you have to satisfy yourself first that his honest thoughts are sincere and genuine.
Hope this helps!