You could hardly write a more stinging critique. Of course, it is perhaps not very smart to go a particular person, but in the Eurocrisis Commissioner Rehn has had a very prominent and public role, even though in his work he has been supported by German, Finnish and Dutch politics as well as by his staff in the Commission.
Such an Open Letter is a kind of angry call, but it must also not be forgotten that the ECB is soon starting with an (apparently tight) Asset Quality Review of banks in Europe, which has not only Italian but also German and Dutch banks worried, so I would guess. Obviously, this is not directly connected with austerity policies but given that the capital flows to the South were a major factor in worsening of trade balances and wage inflation, it is from my point of view good that this aspect of the eurocrisis is in the spotlight.
Beyond that, I quite agree with the arguments in the Open Letter. The only thing they forgot to mention was that Irish and Latvian unemployment is very high despite rather dramatic migration.
But yes, I quite understand why labour unions and the ETUC in particular are angry.