I don't think any of us think language is powerless, pen, and if it were an erudite essay, a philosophical or political paper published in a proper journal then I'd think any amount of pickiness allowable. I think we have got far too picky, however, and object far too often to spoken words which obviously do not have as much thought behind them. In short I think people look for offence too much and that this is badly affecting the prinicple of freedom of expression. My worry is that so often people want to disallow certain words because they find them offensive. That, in my view, is dangerous.
You may be right and maybe Cameron did choose the word carefully for political reasons. Well, yeah, he would, and Harman'scomment were politically motivated too. I don't agree that swarm is dehumanising. It isn't complimentary either. Why should it be?
annieb is quite right when she says everyone can express their opinions and wanting to banish people to a country where there isn't free speech is silly at best, but wanting people to stop using words one doesn't like is not a good idea either. It is the thin end of the wedge against freedom of expression.