I think it is because "lie" implies a falsehood you could disprove, say in court. "Misled" implies a judgment that the president told a technical truth that he intended to be misleading. It could get confusing if you said he "lied", then he showed you how, technically, what he said was true. Falling back to a weaker "misled" at that point would take a lot of air out of the argument.
Well, reporting of politics shouldn't necessarily be politics. There is no reason to stoop to the low level of politicians when you call them on their bullshit.
> Politics is full of that sort of indirect language.
Politics may be full of that sort of language, but why are media? This is not North Korea where journalists have to fear punishment for insulting the supreme leader. Or is it?
By changing the definition, or narrowly defining it, they can exclude all of the great new forms a journalism from the protections that 'journalists' provide. The next step would be a government license for 'approved' journalists.