The question of ethics is important & full of interesting details. It is maybe not the easiest to discuss in terms of short forum posts. As Akseli says in the interview I'm going to quote below, there is quite a bit of thinking on these matters behind the Robin Hood intiative, including several books. 
Anyhow, I myself would put the matter in a series of layers.
For me, personally, a crucial insight was when someone from RH pointed out that there are no "financial virgins" (the there is no outside argument). If a person uses any type of fiat money (euro, dollar, etc.) they are engaged in financial markets. If a person has a bank account, a credit card, if there is pension money in a fund; all of these implicate that the person's money is already being gamed in the financial markets. The banks don't keept the money in an account, thet play with it with the best of their ability. The same if a person has a mortgage. Even more: when a person goes to a store (at least a chain store) and buys something, again, the money does not go into the vault of the nice shopkeeper; it goes to the financial markets. Actually, it has always already gone there, in terms of the future expectations of the success of the store that are bought and sold on the financial markets. The financial markets are already implicated in the pricing of goods, so just deciding what to buy on the basis of price information is engaging in finacial markets. Even watchin a google ad on a webpage is an act that is already financialised.
This layer can be crystallised in the slogan: "There are no banks, just other people's hedge funds." (Like there is no cloud, just other people's computers).
Of course it would be possible to live without fiat money. I have some friends who do that, and have utmost respect for them. But if one uses fiat money, then it is very very hard not to be implicated in financial markets. It's like they say about politics: you might not take an interest in financial markets, but they certainly take an interest in you.
The second, "deeper" layer is that RH is an investigation in ethics, an ethics that does not, at the outset, accept the received notion of the "good". Akseli has put it quite well:
Pekka: What is the ethics of this?
Akseli: We place our tax to all instruments in which we see
financial oligarchy move. It is a shameless ethic, a scandalous ethic,
which binds itself directly into politics. It is an ethical order that
perhaps goes beyond the Greek and Christian traditions of ethics, a
post-ethical ethics and post-political politics that corresponds to our
subjectivity and situation.
Robin Hood is not a moralistic organization. It is not an
organization of the ‘good’. We make no promises of the ‘good’ around
which we would organize. And we are trying to not be an ethical
organization either. Production of ethics – of the conditions and
environments of our action and thought, of the habits and rules that we
follow as if our ‘second nature’ as Aristotle put it – has become an
important method to exhaust the potentiality of our action. We are
trying to break out of this form of control. Our ethics is about
reopening the field of possible.
So Robin Hood ethics is about being able to take action upon oneself
and others. Ethical subject is a subject that is capable of taking
risks, posing a challenge, introducing conflict and division into
community, and of governing oneself and others in a situation of
conflict. Our ethics has to do much more with combat and politics, than
with being nice and responsible, doing what is accepted, staying in a
place assigned to you. The ethics of Robin Hood do not include such
aspects. It is an ethics closer to a poetic, as our philosopher friend
Juha Varto has beautifully said.
Poetic originates in the idea of being in work, doing something,
staying operational, and at the same time aiming at an outcome that is
anticipated but not yet known. Poetic is close to poiesis that is in
Aristotelean Metaphysics a part of praxis, appearing just after the
praxis is divided into theorein and practical interest; in practical
interest there is a need to get some tangible outcome, in theorein even a
thought or a change of mind is enough.
Which brings me to a third layer. At least for me, the commons – one of the main goals of RHC – is not a value. I don't think values "cut it" in terms of the ethical work that needs to be done. The commons is/are an existential space for some of the subjectivities that I want to cultivate.
Back to the real world. Yes, the parasite may very well recommend stocks in arms companies or dirty energy companies or the like, and the RH portfolio may, accordingly, hold that kind of stock at any given moment. This is not ethical investing, I hope our info makes that clear. Why not? Because that is not a problem that needs solving; there are a lot of ethical funds with different criteria already. RHC is a tool geared towards a different problem and a different problematisation: what could an investment bank of the precariat look like?
