Lol.. the devs allow us to export the combat log to a text file. There is no use for that except parsing. They clearly allow us to read combat logs and determine who is bad, its peoples poor treatment of others that is the issue.

And no you can't always detect it, someone could easily have the parsing file uploaded to dropbox and have another computer parsing it.
or like most MMOs, just rename the .exe and they can't find it anymore.

I mean I could claim I just added up all the numbers in the combat log and you looked bad, get out.
OR i could say look at the threat meter your bad, get out.

Harassing someone is never ok, but not wanting to play with horrible players is a reasonable idea. Getting replaced or kicked from the group is not the same as being harassed.