The most straightforward reason for this at least somewhat surprising action on the Islamic State's part is that Representative Ellison and Mrs. Weiner are American government officials (She was and will be again next year in some capacity after Hillary Clinton is sworn in). Plus she is never burqa-ized or veiled and never covers her head, and she's married to a Jew. So I guess I get why al-Baghdadi's boys want to gang-rape and decapitate her.
As to Ellison, it beats me, unless they're condemning him for not having whipped out an Uzi and mowed down everybody in the House chamber the moment he was first sworn in nine years ago.
ISIS, for their part, isn't elaborating much on their justifications:
ISIS has issued orders to kill Hillary Clinton aide Huma Abedin and Representative Keith Ellison, both of whom are Muslim.
Abedin and Ellison are on a list that also names officials in the U.S. and around the Western world, according to the Site Intelligence Group.
They're accused in the magazine of committing "riddah," the rejection of Muslim beliefs, according to USA Today.
The orders came in Dabiq, an English-language magazine from the terror group, the Hill reports.
So pretty much what I said above. Which suggests that ISIS only knows and recognizes violent jihad and considers all the other aspects of it (jihad by deception, or Taqiyya, jihad by immigration, as in Europe, cultural jihad, etc.), the latter of which would seem to include the Minnesota congressman and the Empress's right hand woman. The latter of whom played a significant facilitating role in the Muslim Brotherhood's complete penetration and subversion of (or alliance with) the Obama Regime in O's first term. One would think that would register with Islamic State leaders - i.e. maybe Mrs. Weiner and Representative Ellison are simply deep cover agents for Allah, in the heart of the infidels' highest governing councils, serving the Global Caliphate in their own way.
I guess that's the difference between not being subtle and not being capable of subtlety. "When all you have is a scimitar, every problem looks like an infidel neck". It's reminiscent of Captain Spock's critique of Khan Noonien Singh's space combat abilities in Star Trek II: The Wrath of Khan: "His pattern indicates....two-dimensional thinking".
But by the time ISIS would get around to beheading U.S. legislators and White House staffers, they would have no need for subtlety, even if they were capable of it.
I doubt either of them are losing an inordinate amount of sleep over it. Mrs. Weiner is more alarmed about becoming an Emailgate casualty anyway, and after all, we're all on the Islamic State's kill-list, one way or another.