In L'Existentialisme he writes extensively how since we are born free, condemned to be so in fact, we are only shaped by the actions and choices that we make. With this isolation, does he destroy the idea of placing 'fault' on others?
At the most basic level - the answer is yes. It is 'bad faith' to blame others for anything. However, Sartre was not stupid. He grew up during - and spoke out against - Nazi Germany.
To not place blame on another is a place one stands such that one can be completely free to be responsible for everything that takes place in ones life.
In the same way Thích Nhất Hạnh has said "I am responsible for the world" (unfortunately I couldn't find this quote, so it is not word-for-word accurate, and comes from my memory), Sartre would say that we are responsible for the world. Being Responsible can include blame, but the type of blame it includes is not made up of petty, miserable, self-serving grievances; but rather a greater sense of intolerance toward that which attempts to interfere with the ability of men to act as responsible self-determining agents.
In this sense, we can understand that although Sartre found 'fault' with the actions of the Nazi's, his finding 'fault' was not done from a lack of responsibility, but rather from a greater responsibility.
If we understand responsibility at the lowest common denominator, then we have no shot at resolving this powerfully. One of the best definitions I have heard for what I will call 'Existential Responsibility' comes from Werner Erhard, and is as follows:
The willingness to be cause in the matter of one's life.
With Sartre's idea of "Condemned to be free", we are responsible for not only our choices, but are responsible for choosing for everyone. For what is good for me is good for everyone. However, everyone is free to choose, and the reason behind our choices is simply the fact that we chose them. So it really depends on your definition of fault. Is fault the responsibility one holds when they are the reason behind your choice or is just a feeling of responsibility?