Let everyone have a home, eat and drink as much as they need, receive proper education and healthcare, and thrive working for something they see interest in not a paycheck/boss and you'll see terrorism will be entirely rid of.
In the meantime, i agree it's a reasonable expectation that people can exchange money freely with the caveat that there should be taxes. As much as i hate taxes because they will fund police terrorizing my neighborhood, big corporations for their next nature-destroying megaproject, and cameras everywhere in the big cities, they are important as long as we live in a capitalist system to ensure we have basic public services.
A system like GNU/Taler is really interesting because it promises buyer's secrecy while retaining public accounting for receivers so that they can be subject to taxes. Cash is better of course as anonymity is guaranteed on both sides, and that's precisely why the chief scammers are pushing for the abolition of cash... so much of informal economy/solidarity would disappear overnight i'm having nightmares over it.