Some of my friends use their Facebook account to express their outrage about things in the news. Often I "hide" (now more benignly called "Unsubscribe from") these people because I find their opinions either: valueless distraction, poorly researched, or socially inappropriate. Sometimes a position is called Nazi-like or related to Hitler.
I think this "Analysis of a Typical Facebook Debate" posted by 22 Words is pretty accurate.
I have been reflecting on this and have tried to approach this freshly and even-handedly. In the end, I think Facebook may be worthwhile for debates if one doesn't not alienate the people you are hoping to engage. Hitler references, while useful for conjuring moral outrage when it is needed, may breed more violence and hate.
Maybe Facebook is a decent place for serious discussion. Facebook (and other social media) is something of a public square where moral discussion that involves lots of people takes place. One could argue that it would be better for people to engage in energetic participation in other venues (town halls, magazines, journals, classrooms, churches, guilds) where the level of discussion may be, but is not necessarily, more careful than Facebook. But in these places, very few can talk and much of it is quasi-anonymous.
In our highly transitory culture where people go away to college and pursue jobs wherever they may be anywhere in the world, Facebook and other social networking is a means of resisting that damaging social dispersion that makes everyone feel that there are few people who know you because no one around you today knows where you came from and what you have been through. The people of your past are people who it is worth discussing things with on a moral level. Hence, Facebook may be an appropriate venue for discussion of religion, money, and politics despite my usual disgust with it.
I suspect in our relativistic culture that values tolerance above all else,"Hitler" or "Nazi" are among the few words that provoke moral reflection for most people. But they may provoke more ignorant hate and violence. In order for the public to pay attention to any moral argument, one has to tether it to some moral absolute that is quasi-universally accepted. Most people believe Hitler=Bad. So if one can connect what they find morally-problematic to Hitler, they have anchored it somewhere solid. People in our culture are flailing in a relativistic abyss looking for some handhold. (As someone writing a dissertation, I can't help but footnote. I'm attempting to follow along the lines of the largely compatible analyses of our culture of moral reasoning depicted by some of our best Christian minds: Alasdair MacIntyre's After Virtue and Three Rival Versions of Moral Inquiry, Charles Taylor's A Secular Age, Lesslie Newbigin's Foolishness to the Greeks, C.S. Lewis's The Abolition of Man, Rowan Williams's Lost Icons). As Christians, we have the more adequate, interesting and challenging source of moral reflection: listening to the God of Jesus Christ as richly depicted in the Scriptures.
Despite the fact that it might "work" in public discussion to demonstrate the consequences of decisions or ideas, one should bear the following in mind. Using Hitler is unquestionably a guilt by association ad hominem argument that will destroy the credibility of the user if they cry wolf/Hitler too many times especially because it is often cheap and the analogy tenuous. Furthermore and worst, associating someone else with a Hitler-like position may incite World War II Allies-like violence against that person. If you insinuate that someone has Hitler-like intentions, those who are persuaded by you, may attempt to be violent to the person you originally attacked. If that is not your intention, do not make the Hitler comparsion.