I think this illustrates why it is in fact about responsibility, and thinking about it as blame gets you in confusion.
To extend your example: Bernie Sanders as a citizen, and further a politician, acquires an amount of the collective responsibility for the countries actions in the Iraq War. Bernie Sanders as an activist has more than discharged that responsibility by actively countering it.
A citizen who has done nothing to mitigate or counter the actions is left only with the share of collective responsibility; however large or small that may be, it's real.
To extend your example: Bernie Sanders as a citizen, and further a politician, acquires an amount of the collective responsibility for the countries actions in the Iraq War. Bernie Sanders as an activist has more than discharged that responsibility by actively countering it.
A citizen who has done nothing to mitigate or counter the actions is left only with the share of collective responsibility; however large or small that may be, it's real.