I think that the connection between making sausages and the making of the Treaty of Versailles is a valid one. The idea intrinsic to both is that the process of composition can be a stomach churning one. In order to effectively see both through, one has to be willing to endure some fairly disgusting ends. The condition of making sausage is highly relevant to the condition of making the Treaty of Versailles in this light.
Certainly, I would suggest that Wilson's hopes and aspirations in constructing the treaty endured some stomach churning ends. On one hand, the idealist that Wilson was entered the negotiations with a desire to treat Germany fairly and to ensure that peace in one's lifetime could be realized through open and honest discussions in which no one was excessively punished. It was fairly disgusting to see that his negotiating partners in the Allied Forces did not hold the same view, as their desire to saddle Germany with much of everything in terms of blame guided their discussions. Wilson also had to see his hopeful promise of ending secret alliances twisted, as secret agreements had already been made between the surviving European powers. Wilson had to see his hopeful ideas, rooted in idealism and promise, twisted and mangled into an agreement that ended up becoming more of an armistice than a real treaty.
Wilson's plight certainly echoes the idea that the vices of peace such as caution, manipulation, and mistrust are better not to be seen. They are better to be done in private, similar to the process of making sausage. In the comparison of both processes, one sees the more seedy and disgusting elements, ones that are better off being concealed from others.