This time, I have to agree: the "Easter Worshippers" definition was quite strange. A fairly accurate description of the events could have been written down in two lines, like this:
"Nearly all victims were Sri Lankan, many of them Christian worshippers
attending Easter Mass. Dozens of foreigners were also killed". (AlJazeera)
This is Twitter's lenght, too. This was not used, and I have to say that I would have said "Christians" in the Obama Twitter, because that was clearly the main focus of the attack. This, coupled with the political situation in the US electorate and with the fact that muslims are an interesting demographic to target in many of the historically key states for the presidency (2020 is just next year), leaves many, many doubts on what the reasons were for that awkward choice of words.
Also, I think we should get away from Twitter, it allows people to conceal things. Had it been a statement with no limitation in lengths, the choice of words would have been an overt statement, as a diplomatic, neutral statement would have been possible. As it is now, they could well say: "length was too short, we had to make a choice".
Twitter takes away our ability to expand on things, and our chances of reading the real thoughts behind the words; and by doing that, it generates divisions and misunderstandings and anger.