That's a false dichotomy as not all of the taxes you pay go toward national defense. He sees a closer connection to actively (and willingly) working on systems

That's a false dichotomy as not all of the taxes you pay go toward national defense. He sees a closer connection to actively (and willingly) working on systems that could be used to oppress people in other places than the 50-someodd percent of his Federal taxes finding their way into National Defense spending (which, by all accounts, he probably wouldn't pay if he had the choice). Even if that wasn't the case, the argument can simply be "why contribute even more to the military war machine than I already have to," which isn't at all an unjust argument. This argument also presumes there's no barrier to simply changing residency of country, when in fact, it can be very difficult to get a visa, let alone a job, for a militarily neutral country like Switzerland.