You can defend it, though it doesn't matter much.
As a carrier commander I did this:
Flew over to the ambasadors ship, then a bit further west to get between them and their attackers.
In briefing set up capital ships to form a semicircle around the ship, in true form they all arrived late
You have to deal with 4 Destoyers and a swarm of fighters, I only saw 2 Destroyers though - the other two never entered the battle.
After I arrived at my defensive point I scrambled all fighters.
By this time the enemy was materialising, so I could direct most of the groups to engage after 3 of them had formed up. Proceeded to send new groups out until a second set of fighters approached from the North (unexpected!). Scrambled one flight group just launched and three more to defend the ambassador - though the enemy fighters don't do substantial damage if only a couple are hitting it.
At this point the fighter furball had crept a bit closer to me and the carriers cannons were firing sparodically, I took this as a sign to move away a little towards the ambassadors ship.
It was then that the destroyers started moving, and the thunderbolts were launched.
Unfortunately they did nothing more than irritate the destroyers however it seemed to confuse them - the destroyers moved towards the ambassador, then turned towards me, then turned North.
Finally some capital ships of my own engaged, and torps, lasers and point defence cannons filled the sky focussed on one destroyer.
After it took an impressive amount of punishment it blew up, and everyone moved towards the next destroyer (which had turned away from the fight?). This one took about 5x longer to get rid of, as nobody had torp's left!
The fighter battle was being won by sheer numbers in the main furball and achieving inconclusive results near the ambassador (a couple still shooting at it, the rest chasing my fighters around) so I sent a wing of full strength (most groups had lost one or more fighters), good health falcons over to help and launched the last couple of ships that had finished maint.
Not long after the area was clear of hostiles, casualties being an assortment of fighters and a few bombers that had crashed trying to land.
My carrier did get in X-Laser range for a while, when the first destroyer turned side-on for some reason. The second one was a bit too far away.
One funny thing was an enemy fighter lasting the entire battle quite near (but just outside cannon range) of my carrier.
It seems that something had knocked its engine out, possibly a missile from one of the fighter groups, and it spent the entire battle spinning on the spot - was one of the last ships to die
So yes you can defend it, but you have to apply overwhelming force. If the Destroyers actually engaged things would have gone somewhat worse as they shred capital ships which get in front of them :/
- Deathifier