Also, I answered like Samira, with the same thoughts behind. But there is also more, there is the question of the character himself/herself. I played a character that would be completely puzzled as to why war deccing over those things. Some other characters would definitely not let the insult be unanswered and would go completely berserk until the insult is washed by blood (<3 Silas, and I still hate good old Aldy for diplo-ing out of that).
Each situation is really unique on its own. Let's say, Synthia, that in your example the startup corp collapsed under the weight of the war. Some could say that maybe it's for the better and that corp was already started on a bad basis if it cannot even stand its first trial of fire. Some could also say that the war was completely out of proportion, especially if the people inside this corp were novices and not grizzled vets. Was the war too harsh on the players behind, costed them basically everything, all the hours they injected in the game, or whatever just made it a terrible experience for the players behind to the point they just got disgusted and quit. Well, you can say what you want now at the top of your grizzled vet experience, but a lot of people would react quite differently with just a few weeks ingame behind them. There is always a threshold, a breaking point, where the player will just stop having fun and will leave. Be it due to griefing, wars, or just boredom, reasons are plenty. And ICly, the goal of a war is to crush the enemy to ashes. But OOCly, it can sometimes be different.
This is a rather complex issue imo.
I faced the exact same thing that you described a few times, and one that comes in mind is when I lead AM alliance into a totally RP/IC war over a gallente corp living in Solitude that were boasting completely IC things about gathering intel on us. Well, we had a lot of new blood with new corps in the alliance and we thought it would be good to revive the alliance roleplay while at the same time bringing all that new blood together, and what better than a war - a RP war ! - for that. We thought a lot before doing it thought, and that totally OOCly, because the corp in question was actually not doing very well and most of their activity had dropped to abysmal levels. So, an alliance of over hundreds members deccing a dying RP corp full of carebears, what ? 10 active members ? Like, 5 vs 1 ? We really feared that we would just crush their corp and cause a lot of bad blood OOCly behind. Well, they deserved it, right ? Probably, but still, the outcome was still not good to have.
Well it turned out that the campaign turned very bad for us after a few first good days, and due to various issues (logistics, all the vets in vacations, etc), the target corp actually found a lot of fun in skirmishing and playing with our noobs, while being total noobs themselves, and they had great fun. I think by doing that war we actually saved their corp, which lasted then for years, grew in numbers, and got involved in a lot of Syndicate/Solitude pvp.
So... It's very hard to tell, what's wrong or what's right to do in such cases. I would just say that if you happen to war dec someone, the best bet can sometimes be to moderate a bit the victory at all costs syndrome (which often involves a lot of OOC tactics to win anyway), and try to actually focus on the fun behind rather than the win. Especially for RP, where focusing on the (good) IC drama and the character development, and thus, the fun, should always take precedence over winning at RP.