There are two mass held public opinions on this subject. The first, that there is nothing wrong with onlining, the second, that it is a complete and utter evil. I dissagree with both.
In my opinion onlining is an act of war. Nothing more, nothing less. Certainly, it is dishonerable and very agreesive, not by any means the same as non-online attacks.
On the other hand, it is not a mortal sin. It doesn't instantly warrent death, like killmongering, or the killing for pleasure of the upper ranks(which doesn't really have a name).
It certainly warrents heavy retal from the person, and possibly from his allies. They may want to resort to other less then honerable options (mass murders, onlining him back), or just smashing the guy into the ground every day for a few days. Yet is by no means as bad as killing with no reason. There are two resons for this.
1: While onlining can do major damage to a warband, an alert person can catch it pretty quickly. If you're attacking and your land is going down, that's a pretty good alarm right there.
2: Even if someone does take major damage, it is highly unlikely that it will damage them permenantly, within a run or two, they'll be back to where they were before. It's not hard to bounce back, especially not on BFR.
However, just because I don't belive onlining as serious as killing, don't think I belive it to be ok. As I stated above, I don't. I belive it warrents retal, and, repeated, unprovoked, onlining may warrent death, at the hands of the victom and their allies, or, if necessary, the community.
To sum it up, online attacking is a declaration of war, and a very nasty way to do it, I might add. It's not as evil as some of you seem to believe, yet by no means is it acceptable.
-Ruddertail