After World War I, the main reason Britain and France did not support President Wilson's peace plan was that they

Wanted to punish Germany.

Wilson's plan for peace included a fair response to Germany which Britain and France could not allow. They were angry and bitter after a long war which destroyed their lands. They wanted Germany punished for their actions in the war. Wilson wanted to create a democracy in Germany but also allow them to maintain a military and not have to pay heavy reparations. Wilson was not listen to and eventually left the treaty negotiations early.