Well, it's a manifesto. That's kind of what a manifesto is - a statement of your positions. If your manifesto is not going to devise those from first principles, then "we believe" isn't a bad way of putting it. (And even if it does devise them from first principles, you still have to justify your first principles.)

That's not a "religion" by normal definitions, but it's perhaps a religious way of stating it. (It could in fact be a secular religion, but the wording of the manifesto isn't enough to show that it is.)