First off Matt Lewis is currently a fellow student here at Queen Mary, University of London but I don't know him that well (the curse of these days spending very little time on campus outside one's own department) having only met him on a few occasions. I can't recall ever encountering Richard Lowe at all and think I've only encountered Flick Cox from afar when she was elected to the national executive of the National Union of Students (she stood claiming to be an independent but was actually a member of one of the ruling factions - see In the world of Adam Nazir Ahmed Teladia: NUS NEC elections).
I don't think Matt meant to cause harm or offence and indeed as many others commenting on this have noted there are many other people who've similarly made bad taste comments and actions without having them dragged all over the media or getting back to the victims and their families. But that doesn't mean it wasn't a stupid thing to do and I have no doubt of his depth of horror at the consequences coming back upon him.
One point that has been rather overlooked is the comment (see Tory Bear: Sick):
Im quite glad about that, I would hate to have to end our friendsship when I become and MP because you had pulled a Prince Harry!!! LOL xThat's not the comment of someone being a friend, that's the comment of a scheming (and deluded) careerist.
But I will also be blunt - the reason this became a story and offended the McCann family is because another blogger took it upon themselves to act as judge, jury, executioner and town crier by running the story on his blog. That is also an act that causes offence to people.