If I refuse coms because I don't want to talk to you, and you kill me for it, as happened last night, that is indeed random PKing. Embrace what you are... terrorists.
The response is simple. If you can get along with them and still make a profit (as is suggested by their response to my post upthread) then it's not a problem. If you can't then either take 'em on or go work for a faction opposing the empire in a mode where they can't reach you. To be a terrorist you have to be able to mount a credible threat and within the game mechanics as-is they can't.
Personally I regard it as enhancing the game experience if one can encounter groups like this and make the choice to either get along with them (even without becoming affiliated) or defy them and risk the consequences.
I'll work for whoever pays me the best. If I get the best risk/reward scenario by trading at skiff port then I'll trade there, aid their cause and - at the same time - gain a bit of empire rep. As far as rep is concerned my goal is to be friendly/allied with all three majors. Anyone doing business with me can trust me, and I'd like my rep to reflect that