Thank you for writing this thoughtful post. There was one point where I felt that I do not agree with you.

“The aftermath of Monday’s suicide bombing – the widespread rioting and burning – are characteristic of the kind of reaction and vandalism that follow sectarian attacks.”

Consider the systematic nature of arson and torching of shops and buildings in the Bolton Market by masked miscreants who were all dressed in black and came prepared with cutters and inflammable chemicals. All of this was captured by security cameras. It is hard to imagine that they could be the Azadars (mourners) with those accessories ready who somehow knew beforehand that a blast would happen and they would have the opportunity to steal and torch those shops.

Consider also that the “reactionary violence” by “angry protesters” – as some news sources framed it – happened only in the Bolton Market. If the reactionary violence was indeed caused by irrational impulses of angry protesters, then the systematic arson and property destruction should have happened at multiple points in the miles long procession on the M. A. Jinnah road. The plotters surely screwed up this part in their planning.

The blast and its aftermath were clearly well-planned, perhaps coordinated among multiple groups whose diverse interests all converged into making it happen in Karachi.

S, you may also want to check out the following two links. The second addresses your question/concern about stopping the processions for security reason.

http://insidesectarianism.blogspot.com/2010/02/talking-points-about-ashura-blast-in.html

http://insidesectarianism.blogspot.com/2010/02/muharram-blasts-in-karachi-why.html

It is very very sad the way everything happened. Although after reading this blog, http://yello.pk/blog/fazarcane/the-day-karachi-lost-its-mind/8587, I had goosebumps all over.. :S

You cannot ignore these facts easily.

http://thelondonpost.net/SQ31dec09.html