Every fuel , including HHO is the road to hell. If you need to refill tank or battery you are victim of possible TAX PAYOFF and you don't see it as a SIN done to nature, but rather something natural.
People start screaming only if the stupidity of tax reach their brain cells, which is very hard to do. I think they can even accept tax put on water as a fuel.
That is why there is more opposition to Joe cell running engine which takes ions from air then to HHO (made commercially in small scale in Japan for example).
Simply - you cannot (yet) tax air.