The effectiveness of this strategy is not so much mocking Daesh. The strategy can be effective by adding noise to their signal.
This works in live protests as well, this is the electronic equivalent of a protest I saw in college. A white supremacist was giving a speech at a public library in central Illinois. Protesters out numbered actual audience members 2 to 1. They proceed to sing children's songs and play instruments. This blocked the message of hate helping to prevent further recruitment and coordination.
I can just imagine someone not already well informed walking away with the impression that the nice rational people who only wanted to talk about their ideas were being drowned out by the mob literally acting like children.
Have you ever tried debating with bigots? Both sides end up talking over each other.. I think it makes brilliant sense, to sing songs, hymns, etc and make the other side look dumbfounded and unable to respond..what do they do sing metal ballads about how all other races should be slaves?
And it's disgusting to have a go at someone's wife because of the beliefs and actions of the husband.