This is what I did to insert the CSRF token in backbone requests. This works with django.

Backbone.sync_csrftoken.js

var oldSync = Backbone.sync;
Backbone.sync = function(method, model, options){
    options.beforeSend = function(xhr){
        xhr.setRequestHeader('X-CSRFToken', CSRF_TOKEN);
    };
    return oldSync(method, model, options);
};

Thanks! Finally something that works!