There are also posts in which not a specific person but an entire group is being slandered. Like that person some years ago who kept on writing posts in which he harrassed bisexual people (in general cause all of them were bad in his eyes). Any kind of insult, specific or not, subtle or not, can be a reason for flagging. But in some cases, the flagged persons themselves don’t see what they did wrong. That doesn’t necessarily mean that the flagging was done with insincere intentions. Therefore it might be good if the flagger had the option to clarify the flag anonymously. Not just “it’s spam/inappropriate/whatever,” but specifically pointing out the words that triggered the flag. We can already do that, but not anonymously and that probably stops a lot of flaggers from doing so.
Personally, I would never flag a post just because I didn’t agree with it. In that case, I would either state my opinion or ignore it. But if any person or group, specifically or in general, is being insulted/harrassed/badmouthed/put into a bad daylight/etc., even if it happens in a less obvious way, then I do see reason for flagging.
That said, there indeed is also flagging without good reason and some of it is granted by the staff as being valid cause they usually don’t take much time to really look into the matter.
Then no one would flag anyone anymore. Or the flagged people would start harrassing the flaggers.