Indeed, to really address someone's arguments well enough to try to change their opinion takes a lot of time and effort. The question is, what is the benefit to you of doing that? If it is a real live friend that you are going to spend a lot of time with it may be worth the effort as they become perhaps a more enjoyable friend to spend time with (e.g. a friend who keeps telling you what a Great job George Bush is doing may begin to grate on the nerves). However, a stranger on the Internet you only know by a fake name, if you refute their arguments and win them over, it is not clear that you gain much. They go away. So, in casual conversation such as in these responses here or in Reddit, where everything is anonymous and long term relationship is not likely, it is easier and perhaps more satisfying just to call them an ass. Perhaps this would change in a reddit embedded withing a facebook where there is more relationship context for the conversation and where perhaps, there is more to be clearly gained by changing someones mind about something.