To give you my answer in advance, the stress occurs because it suits the narrative that the US faces the implacable enemy of Terrorism (i.e., what is normally considered a tactic, raised a metaphysical notch or two to a concept that subsumes a large number of entities into itself).
First, some news. Late yesterday there were puzzling news flashes that the surviving Tsarnaev has been communicating with interrogators in writing, in spite of being in “serious condition.” CNN now explains that the interrogation has occurred during “sedation holidays.” These are periods where the sedation of an ICU patient is temporarily suspended, normally so that doctors can “can ask patients questions to assess neurological and cognitive functioning.” (If you are wondering about the medical ethics of allowing such periods to be used for non-medical purposes, so am I.)
Now, it has not been possible to escape reports in the MSM that the now deceased elder Tsarnaev brother had travelled to Russia’s North Caucasus region, home of separatist movements that, like other oppressed peoples who have not had access to normal weapons of war, have at times targeted civilians, thus virtually automatically qualifying for the US State Dept.’s designation of “Terrorist.” It has not been possible to escape reports that he had viewed Islamist videos. This ethnic/religious slant has also turned up in a number of recent FDL diaries (here, here, here, and here; and as a measure of the extent to which the stress has penetrated FDL consciousness, the last diary is on the Recommended list as I write, in spite of being flagged for impugning a religion as such).
What IS possible to escape, although also possible to discover, is that the younger Tsarnaev brother is in every outward appearance a normal college kid , one who intermittently goes to classes, socializes, and works out. (The point has led to at least one tongue-in-cheek assessment that he is “hot.”) Of course one can convert this realization into a feeling of “gee, you never would have known he was an Islamic terrorist,” but why would you do that unless you had already determined before a trial in a court of law that he was guilty, and further, that his family religion was the operative link in the chain of events?
It is now well known that the FBI cleared Tamarlan Tsarnaev of any terrorist connection in 2011, so that any alleged radicalization was after that. But assuming that that indeed happened, why would one expect the radicalization to be via any other route than one connected to his family lineage? The Oslo mass murderer of Muslims Anders Breivik considers himself to be motivated by his Christianity, but that religious heritage does not figure into most discussions of his case, so why insist on it for Tsarnaev?
I can only think that the answer is because we are conditioned to do so in all cases where Islam is even remotely connected to the case.
Some miscellaneous points:
*Despite certain reports of a possible terrorist “cell” in which the Tsarnaevs took part, police claim that they were acting on their own (h/t marym in Il).
*The principal North Caucasus separatist movement has denied any connection to the bombings (h/t yellowsnapdragon).
*As is now well known, the parents of the brothers believe that they are being falsely accused. Some commenters on FDL posts on the subject have expressed similar suspicions (for example, wondering what happened to an early report that someone else robbed the 7-11 and killed the MIT policeman). I will not endorse that position here, but, particularly in view of the history of the FBI, I do take the position that Dzhokhar Tsarnaev is innocent until proven guilty in a court of law.
And he is an individual person first; a member of some ethnic, religious, or other group second. That is how we think about people in the U.S.A.