I hardly think correct use of a technical term (in this case, in the field of law) is an "abuse of the language"; see http://dictionary.findlaw.com/definition/assault.html

The rest of your argument seems to boil down to the same behavior would have been fine if it were consensual, and that kind of situation makes it easy for the guy to misinterpret consent. This reasoning is absolutely ludicrous. First, he kissed her, then "I tried to push him off, and told him I wasn’t interested (I may have been less eloquent, but I don’t think I was less clear)", then he jammed his hand down her underwear. How would that be misread?