Since when has "be an adult" become synonym with "be complacent"?
As far as I'm concerned, the OP has every right to report someone with malicious intent. And intent matters, even in matters of law intent is extremely important before deciding on a guilty/innocent verdict, let alone a sentence.
One thing would be a slip of the tongue, a conversation between person's where a third might accidentally be spoiled - sucks, but it happens.
The other is someone going out of their way to ruin someone else's fun, unprovoked and just because (aka, malicious).
Whether it falls directly as harassment, whether it breaks the TOS or not, I'm not completely sure. But that's what the GMs are being paid to do.
So don't feel bad for reporting someone who's wronged you. Let the GMs figure out what to do with it, that's literally their job.