> Immigration plus no welfare state was vastly better than the alternative of starving in ireland. It's also vastly better than being beheaded by ISIS or being paid 200rs/day in India.

Sure, but so does immigration with a welfare state. What does the welfare state have to do with that? If you'd say that the welfare state increases the cost of accepting immigrants, that may be true, but people living in a welfare state are usually willing to pay that price for what they believe is a more pleasant society. I don't think free-market people are any more willing to accept immigrants for their own free-market reasons (e.g. they're willing to settle for less so they lower the wages overall, and most people are employees rather than employers).

> I'm also confused by the collective responsibility you seem to allude to. How do you determine which groups this responsibility adheres to? Can "the Jews" rather than "Europe" also be collectively responsible for things?

That's a very good question that is the subject of much debate in ethics. But the first thing to note that in this case there is no legal responsibility or any sort of coercion, so the philosophical burden is lifted a bit. If there's no obligation we can resolve the matter with a simple feeling. If you feel responsible -- act; if not -- don't.

But if we were to discuss the matter more on principle, then you can try to answer the question in general (see [1]), but I prefer a more pragmatic approach if "philosophical shortcuts" can be made, and I believe that in this case they can be made, due to these two (particular) factors:

1. The cost of the action is collective (i.e. tax money). While it may affect individuals personally (those harmed by increased crime), that is not any more so than any collective action, like zoning, taxation etc. (contrast that with collective responsibility of the kind that exacts a direct personal price like bombing civilians).

2. The benefit from the harm inflicted is still felt. Most Europeans today benefit (personally, though perhaps indirectly) from their respective countries having looted the rest of the world.

(also, of course, unlike with "the Jews", there really was collective action involved in subjugating the rest of the world)

The extenuating circumstances in this case -- namely that European states were not democracies at the time most of the meddling took place is offset, IMO, by point 2, which makes everything easier. If you possess stolen property that you inherited, you still have to return yet (that's a big generalization and there can be special circumstances, but as a general rule, this is a relatively easy moral call).

So I think that in this particular case, these two factors make it easy to assign collective responsibility, even without resolving the question of collective responsibility in general. BTW, My personal view is that collective responsibility can only exist in particular cases that are very dependent on circumstance. It is certainly more rare than personal responsibility, but it exists because much of human endeavor is done as groups that are more than just a sum of individuals (as we know that group dynamics is a very different beast from personal dynamics). If you reject the notion of collective responsibility in all circumstances, you exclude a large part of human action from moral judgement (I don't believe ethics is by any means an absolute, but as a human construct it is meant to apply to most human actions).

It is interesting to note that even the Bible, which normally places a strong emphasis on personal responsibility, certainly acknowledges cases of collective responsibility (and sometimes punishment).

[1]: http://plato.stanford.edu/entries/collective-responsibility/