Frankly, it is difficult to "address" a subjective opinion without having been given the criteria for a satisfactory answer. But I will try: being a responsible adult includes contributing to national defense.
Your original statement, that "Each capable adult must be held accountable and responsible for themselves in this world," is a subjective opinion--unless you meant it merely in the sense of a truism--and you did not give me any criteria for a satisfactory "counter-argument".
Regarding this:
>being a responsible adult includes contributing to national defense
you are equivocating between two separate definitions of the word "responsible." Being a responsible adult is not the same as being an adult who is responsible for their own defense or healthcare, for example. They can be correlated, but they have different meanings.
But honestly, this form of internet debating you started that derails from the topic and gets into quasi-logical nitpicking is uninteresting and makes me feel like I'm in a high school, so this will be my last comment. Please feel free to reply, and I will read it. But please make the reply have some substance.