Well, how fair would Freespace 2 multiplayer be if a someone found a way to hide in the hull of a Sathani and fire without being hit?
BF2 - and other games of that ilk - is supposed to be a reasonably realistic (well, atmospheric) game with an attempt to bring in some form of tactics and teamwork. Above all, dolphin-diving ruins any sort of atmospheric immersion and degrades from fun. It's like for proper games - i.e. sports - you have the choice between playing fair or playing dirty.
If you're calling BF2 realistic and atmospheric, I really don't know what to say.
(being a multiplayer FPS disqualifies it from both right there) It only degrades from the fun if you're one of the people who complain about the tactic instead of using it to your advantage.
I've seen this sort of behavior in every multiplayer game I have played. When some new trick or something comes up, some people adapt to the new tactic and others throw a hissy fit over it because they refuse to change how they play. This is why we had for example, all the "no fish" idiots on PXO when FS2 came out and the VBB fuss over the usage of anonymous nametags in squad matches a few years later (by Drak and some other squad I can't remember).
As for hiding inside a Sathanas, you can already do that in some sense. Just go into one of the "scale" things on the back of the ship. The turrets won't be able to hit you there.
Here's why it's wrong:
Bunny Hopping and Dolphin Diving cause hitbox and accuracy manipulation that (in the first case) makes the player much harder to hit as the hitbox becomes misaligned with the animation and in the second case, causes this as well as the advantage of having prone-type accuracy the entirety of the time - even when moving around at speed or in the air.
To put it in FS multiplayer terms - it'd be like the enemy ship disappearing in one place and reappearing 10m further on whilst still being able to fire perfectly at you. You have a vastly diminished chance of hitting the ship, and it maintains accuracy all of the time.
If players had been meant to have that accuracy whilst moving then it would have been possible from the word "go". However players are not supposed to have that kind of accuracy whilst moving around. Your accuracy is greatly reduced during a normal jump or whilst walking/running.
Ergo it's a manipulation of bad game coding. It's being fixed in 1.4 patch apparently but untill then it's as good as an exploit in my eyes.
That alone is no reason there is a problem with it. All I see there is making intelligent use of the rules. Who knows, maybe the developers wanted only the players who took the time to master this technique to benefit from the added accuracy. And in any case, there have been unintentional "bugs" like this in other games that have become completely standard tactics over time, like the Quake double jump and the tricording in Descent.
Now if it's going to be changed in an upcoming patch, that's a different matter and something that should have been brought up earlier. Although until the patch comes out, it's still within the rules.