The thing that is happening is that we have diferent communication tasks:
The first one is to expres an emotion but in past as a situation: temía que me despidieran. When you talk about a feeling related to someone else actions you use subjuntive, in this chase is a past situation so you most use the "subjuntivo imperfecto" with the action that cause you a feeling. The next thing "si me oponía" is refered to something real, at least for the one who is talking. Look at this: "si me oponía me despedían" or just the same: "me despedían si me oponía".
Summarizing: a conditional sentences in accordance with the reality uses indicativa, just like the last exaple. To express a feeling uses subjuntivo just likein the beggining. The sentence you chose merge both functions. I hope I've helped.