In the Jubilee, you've got an event that over 1,000,000 people watched live (and hundreds of millions will have watched on TV around the world). To put it together required the help of tens of thousands (both paid and unpaid). It is hardly surprising - deplorable in this specific instance, but no surprise - that somebody somewhere cut a corner in a particularly nasty way. But to tar the other 99.9+% of people (or the organisers, who literally won't have had a clue what arrangements a minor sub-contractor made with a minority of its staff; that level of transparency simply doesn't exist) with the same brush is just ludicrous.
Basically if you take any massive undertaking (private or public) you'll find SOMETHING in some far-flung corner that "stinks" if you really dig hard enough. But it needs to be kept in perspective - if the "only" major issue of the Jubilee is 30 people who had to sleep under a bridge and otherwise got mis-treated by the company that offered them unpaid positions, then it's an incredibly well-run event and that take-away should not be marred by a tiny, fringe incident.