Bees swarm. Bees are busy, productive little workers. Swarm, in such a context is positive imagery.
Which gives me pause. Those who criticised Cameron were the ones who inserted the negative imagery about "insects", the swarm as a threatening thing. This is the hazard with putting words in people's mouths or reading-in intentions which (possibly) aren't there: you either dig too deep, trying to find mud or you subconsciously insert your own fears and opinions into your spin on the quoted speaker's meaning.
However, they extracted "swarm as threat" from the overall context of Cameron's speech: a "mass" of people were "over there" and they are "coming here" - which is what swarms generally do.
People teaming up to do Twitter activism is cooperative working so the bee analogy is clearly what is meant.
Not hypocrisy but contextual flexibility.
Pity I'm not paid by the word!