I read the article on BBC before watching the vid and assumed that it was the main advertising board round the edge he'd kicked and a bit had flown off the side and unfortunately hit the official. Still unacceptable but maybe just bad luck.
Watching the vid though, it's an absolute disgrace. From where he's kicked that little bit of extra boarding, there is no outcome possible other than it slamming into the poor bloke, it's basically all round his legs and only inches away. IMO he deserves more than just a DQ for that, he should be banned from the next ranking tournament as well.
Edit: Maybe even more than that... can you imagine if you were at work (lets assume office job), something goes wrong so you get frustrated, go up to the nearest desk and thrash your foot through it, injuring the person sat there. You'd probably be at risk of dismissal I'd imagine?