There is no way for rebels to avoid negative propaganda by the regime except to surrender.
Obviously you cannot expect the regime to applaud for the revolution. Of course they will label you as terrorists, vandals, and trouble – makers; if they didn’t, it would mean that you and they are on the same side.
If you are worried about the opinion of the population about you, then you can influence their opinion by achieving real results. There is nothing more influential than effective action. And as long as you are doing effective action, of course the regime will demonize you, but the people will know you by what you achieve for them not by what your enemies say about you.