My problem would primarily be that they did it the dumb way, the smart way would be to edit someone's account and give them access to the forums that was a member of the attacking corp (the person would have had to have registered before the war a bit though).
Otherwise, deleting the posts is a bit douchey, making it public not as douchey (easy enough to fix), also would depend on what content was deleted. I wouldn't have an issue so much if the content they deleted was strategic, but if it was like "how to" guides or some shit that were there to help new members or whatnot that would kinda irritate me.
That makes for an interesting (and entertaining) conundrum.
The theft itself I still wouldn't have a problem with - I don't even give two shits about the IC/OOC motivations. If someone steals from me, then it was my own damn fault for trusting them really, since I don't really talk to most players OOG unless I have already known them from another venue, save for maybe 4-5 of you and these forums. If I feel a bit of opportunism and opt to yoink some shit from a corp and high-tail it out, then I will do so.
I could even be motivated in the right circumstances (were I in a large alliance for instance) to make an alt on a different account, infiltrate a corp I am already in, rob that corp's assets with the alt, funnel them into the main, and delete the alt.
Just because I felt like it.
It's a game.
Granted -- I come from a place where even prior to EVE in any of my MMO/Gaming-In-General you didn't hand people sensitive shit. There's no reason for everyone to have access to your top-end T2 BPOs that are now an even greater rarity. There's no reason for everyone to have access to all your T2 and T3 ships/modules.
There's no valid reason that even a moderate number of people get to get their grubby little mitts on anything of value. That's the fault of the leadership if they get all their shit stolen, given the layers upon layers upon layers upon layers of security the game offers.