My trader has honestly not been pirated by a "pirate" in a long LONG time. In fact, the last two hostile encounters my trader has was with a Wilde gunboat and a Phantom HF. Both were instances where I hit the cruise engines, opened up the chat window, and started RPing.
Now, given that they were not normal pirates, my response was a bit different from what it would be for normal pirates. My tradeship mounts a discovery scanner for a reason, and if I see hostiles on the scope while I'm in a lane, I drop out and try to go around. If I don't do it in time and they catch me at a downed lane, well, my response depends. First of all, how far away is the hostile? If it's more than 2k, I'm probably going to try running first, since there's a good chance I can pull it off. If it's less than 2k, I'll cut my engines and be all nice and cooperative. The goal is to get through the encounter without being exploded, and without losing my cargo. Because of this, I'll pay whatever the pirate demands, even if it's "unreasonable". Because really, losing a 150mil ship, a full load of cargo, and possibly lives, is not worth 2 mil, 5 mil, or even 10mil credits.
After the encounter's over, then I run away as fast as possible and scream on the system chat about a pirate, or contact the local police and military.