This topic has been brought up, questioned and talked about so much that it's undoubtedly the most debated topic. Spawn killing pisses people off....plain and simple. Here's what happens,
when you start off this game for the first few weeks/months, you get SK'ed, alot. Gradually, you learn to accept it as a part of the game and give some back (with the exception of Tank Spawn Killing which is a biiggg no no!)
I've learned to take some evasive maneuvers and can usually manage to take off with a circling SK'er behind me with the use of some brakes, timing and some clever use of the buildings (hint: fly low and bank hard between them). Once I'm airborne, I have a pretty good chance at the chase. Ok more than good, I take down the SK'er in every instance
Personally, I don't like to do it but there are certain instances where I have to. When I bomb the base, I will stick around and shoot some reds just long enough to make a clean getaway and if on the way back to my base I fly past a blue team-mate, I will turn back towards the red base to assist them. The other exception is if I note someone SK'ing endlessly I will SK them back and keep them pinned down, you know, for chit's and giggles.