Act only in accordance with that maxim through which you can at the same time will that it become a universal law.
Edit: to address a common confusion: this has nothing to do with imposing a rule on others. This formulation only says that you ought to act in conformance with rules that you would want all others to act by as well.
So, if there is already more support for military that I find optimal, it makes sense not to support it altrough in different situation I might decide differently.
That seems entirely too tyrannical, imperialistic, and egotistical to be practical.
Where does having freedom, humility, and an open mind fit into that maxim? I.e. being willing to accept that all humans (including ourselves) can be misguided, or that someone else could know what is better for them than me?
So there isn't anything contradictory or inhibitory there. Perhaps you are not seeing the generality implied by the term "universal?" The contrapositive here is to not act in a way that assumes other people are incapable of, unworthy of, or disadvantaged by following your example. There is nothing here that implies one can't be humble or liberal. To put it in less gentle terms, the point is that if you don't intend for other people to emulate you, then there is no point to your life in human society.
Choice quote:
"""Do you try to keep others from taking military funding?
No. Mine is an individual testimony, and each person makes an individual decision about how they will spend their life's work."""