Yes, clearly one can construct ridiculous examples. On the other hand, one can also ignore clearly valid cases while trying to construct the perfect solution. Sometimes the real world involves solutions that are merely acceptable. Or even individual judgement calls - hence why we have judges and juries.

But since you seem to think that there is a fully-cohesive, non-circular, objective way to judge what is harassment or abuse, please enlighten me as to what it is.

If you fail to do so, then somebody will probably rape and kill your entire family. <-- Not abusive, because there isn't a peer-reviewed Theory of Abuse available.

edit: Just for the hard-of-sarcasm, the last bit is to illustrate the ridiculousness of the argument, not an actual threat.