Earlier quoted context omitted.
A single message is not harassment though.
You can't make that blanket statement. A single punch is battery. A single genital grab is sexual assault. A single demand for quid pro quo sexual favors in exchange for professional rewards is sexual harassment. A single message asserting that an individual is not right for their job because of their gender creates a hostile work environment, and that's also sexual harassment. Just because there can be cases where a…
A single demand for quid pro quo sexual favors in exchange for professional rewards is a sexual offence, a bad one, and alone it is not harassment. IANAL, though the dictionary definition sticks with me, especially the key words: "multiple", "unwanted", and "intentional".
That's why "harassment" as a word exists, it is to indicate that multiple unwanted events have happened intentionally.
Maybe the legal definition of "harassment" differs from the dictionary definition. If so, a new word for single event harassment needs to be chosen.