Where I have disagreed with you has been over a question of what constitutes discourtesy ... But people can and do make harsh remarks....
I think that we are all capable of upsetting other members ~ often unwittingly. We are all just human & we may become frustrated, angry, over-enthusiastic, etc.
I also think that upset can be the result of misunderstanding, or of taking things personally, where they were not meant as personal insults, etc.
If people go too far, then they may be told ~ but not always publicly.
If I am seen to go too far, then people usually tell me.
And what one person sees as too far, another may see as quite moderate.
Discourtesy certainly isn't encouraged.
But I have had people complaining that someone is being rude, while they are being equally discourteous, themselves, and they simply cannot see it.
I have to make the best judgement a flawed human mind can make, based on the information available. But it doesn't always go down well with the person in question, or their friends.
Sometimes I have spent, quite literally, hours ~ going through threads, and evaluating posts, to see who said what and when, in order to respond, fairly, to complaints and criticisms.
I try to act as a fair and objective mediator ~ even where people have been extremely negative with me ~ but I still get the blame for whatever goes wrong.
And I try not to make a fuss, but, at times, it can be hurtful and annoying ~ which is why I have come very close to leaving on a number of occasions.
Maybe it's good to vent, once in a while, though, so maybe threads like this are a good thing.