I can see both sides of the arguement myself. Perhaps a way to settle it might be on the basis of the mission selected. In some cases this might work.
For example in a Convoy escort/ Convoy raid the conditions of victory are set by the game, I don't think disengagement rules should apply to a raider that fulfills the missions victory requirement even if he leaves the map after doing so.
Now take a shipyard assault. The burden here would be on the ship running fast. It would only be a matter of time before reinforcements arrived so if he was the attacker he would have to finish his mission quickly. If he was the defender, he would have an obligation to protect the shipyard rather than flying around all the edges of the map.
Now conversely, in a mission such as a scan recovery the slower ship might have to pick up speed, otherwise the fast ship would simply run by and scan the data, and depart or if the fast ship was the defender he would be in his space and thus calling up reinforcements.
My point being, the nature of the missions might really be the key to determining who needs to change their tactics rather than preceptions about who is delaying the action. I think most people are divided on this issue along the lines of the races they usually fly (with some exceptions) because each race has its strengtht and weaknessess.
The Hydrans and Lyran likely the two most polar examples, it is rare that you see a Hydran fly over 15 and rare to see a Lyran fly under 20 (unless its Hexx and he has been in the mission over a minute
) To call either one right or wrong in their approach seems silly to me, why not let the missions determine it, would give an additional advantage to a race defending their territory as they would have more control over their choice of missions in homespace. As long as the missions offered were relatively balance for frequency of occurance I would see no problem with this.
I think this issue has reached a new level of importance with the advent of special disengagement rules. Before no one minded losing a mission vs a starcastler so much as they could re-enter the hex. I think of this as simply doing and end run against a static defender. The defender castles and the attacker simply flies off the map and goes around him to hit the target or another target in that sector. Now with the disengagement rule you get bumped for an extended period of time so more careful thought is needed regarding this issue.