*sigh* And again...
Stealth Bombers, on average, get maybe 1-2, maybe even 3 kills. Heck, quite often I see people get NO kills with it, even when used several times. If people are constantly getting 4-6 kills using it, then that's the OTHER team's fault for camping/fighting SO tightly packed together in places where they can be hit by the bombs, not the Stealth Bomber's.
The Stealth Bomber fits very well under Support because that's primarily what it does; supports your teammates by either clearing a path with the bomb run (either by kills OR forcing people to cover) OR by disorienting the opposing team and making them easier for your teammates to kill. You CANNOT compare it to Precision Airstrike, which the ONLY point of it is getting kills for yourself to build up for your next killstreak. It kills and only kills and nothing else, hence why it is in the Assault Killstreak category.
With the Stealth Bomber...
1.) The noise the Stealth Bomber makes right when it's called will usually make people...
A.) Look up towards the sky to try to physically locate it. While they're looking at the sky, they'll be distracted and be less aware of their surroundings, making them more vulnerable for your teammates to pick them off.
B.) Immediately try to take some kind of cover. This allows you to herd opposing players into a fixed location where they'll be somewhat trapped for your teammates to kill.
2.) Just being near the explosions, but not killed, will end up heavily disorienting opponents and deafen them for a few seconds like a more severe Concussion Grenade. This will greatly slow down their speed and throw off their aim, also leaving them more vulnerable for your teammates to pick off when/if they locate them quickly enough.
So basically, getting kills is not the main/sole purpose of the Stealth Bomber like people seem to be under the impression of and it fits well in the Support category. And no, I'm not a Stealth user either (I use Assault Killstreaks myself). People really need to stop with the whole "Support should only be non-lethal" mindset as A LOT of "support" in real life is QUITE lethal...mortar/artillery fire...air support...chopper support...etc.
If people still want to think that way, then they may as well take out the UAV and Care Package from the Assault Killstreak category and move it to Support as they're both, by themselves, non-lethal, thus don't "fit" in the Assault Killstreak category. I'm sure there are a lot of people who think Care Package shouldn't be in Assault, especially with the chance of getting things like AC-130s, Pave Lows, Reapers, etc like that, especially for only 4 kills (3 with Hardline / Pro).