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

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.