Blogposts and newspaper editorials are ephemeral: here today, gone today. They may have a cumulative effect, but only in the aggregate. Not so with works of art, which can stick around for a while; some of them even for a very long while.
We don't know how long Caryl Churchill's insidious little play Seven Jewish Children will be around to spread its poison. So far, it hasn't gone away; on the contrary, it's doing quite well at outliving the blogposts and newspaper critics' opinions explaining why it's antisemitc. Just to make sure, however, the Guardian has just posted a video of it, here. After all, a short pamphlet or PDF file will eventually lose its power to hurt the Jews, unless someone does something to enhance it; even word of mouth buzz must repeatedly be recharged somehow if it's not to die out. A video, however, if done well (this one is), has more power than mere words; if posted prominently on a popular website it may easily enjoy a second lease on life far more potent than the first round, where people read about it but didn't see it.
So this is an example of the Guardian actively seeking ways to promulgate antisemitism, beyond merely slanting its reportage and punditry of the daily events.