Its just a video game.
I know the context of that scene looks like the events on 7/7, but that could be an empty train for all you know. And that shootout outside the partiament is tame, since there was a shootout inside the White House in MW2.
Also in the trailer, France and New York look like they are under greater threat / peril. If you ask me, it seems like Activision held back on the level of destruction London goes through.
Wait for the whole gameplay sequence to be released before judging.