We cannot deny the horrors of the past or the present. But as Kant reminds us:
… however uncertain I may be and may remain as to whether we can hope for anything better for mankind, this uncertainty cannot detract from the maxim I have adopted, or from the necessity of assuming for practical purposes that human progress is possible. This hope for better times to come, without which an earnest desire to do something useful for the common good would never have inspired the human heart, has always influenced the activities of right-thinking people.
E. Kant / Political Writings