Although I don't necessarily agree with including swearwords by default, I will play devil's advocate and say yes, swearwords should be included.
I think the first, most important reason is that swearwords are extremely common words. It is estimated that 0.5-0.7% of spoken words are swearwords -- that's about 90 words per day. For comparison, the common words 'we', 'us' and 'our' are used 1% of the time . So a typical SMS user may be expected to use swearwords a couple of times per day. Not autocorrecting swearwords could be seen as annoying 99% of users, to avoid offending a 1% minority.
If we can have some way of ensuring that users definitely do want to use swearwords, we should not stop them. If the user types 'b******s' accurately, I think we would agree that it should not be changed to 'badgered'. This is how Android seems to work. But suppose the user mistyped one character: should we autocorrect it? Well, if we have data which suggests that the user did want to type the swear word, I do not think we should. That data could be, for example, the user having used the swear word in past SMS messages.
Of course, there will be some people who are offended by swear words. At very least, I think the user should be given the option to enable swearword autocorrection if they wish. Perhaps there could be an 'automatic' option which disables such autocorrect by default, but enables it automatically if the user frequently uses profane words in their messages.
I would make one last point about the differences in attitudes about swearing between different age groups and cultures. It is my understanding that, in general, swearing is seen as more offensive in the United States than it is in the United Kingdom, for example. In the UK, research by Ofcom (about swearing on TV) demonstrates that 93% of 18-34 year olds find swearing acceptable in certain circumstances; for 55+, the figure is 49%. This may be interpreted that swearing is becoming more socially acceptable in modern times.
1 Jay, T. (2009) The Utility and Ubiquity of Taboo Words. Perspectives on Psychological Science. 4 (2), 153–161. URL: http://www.psychologicalscience.org/journals/pps/4_2_inpress/Jay.pdf