Let me see if I can help explain. Being quasi-legal is a balancing act. You have to do all the right things in front of the lawfuls such as the militaries and other civilian corporations while you have to do all the wrong things without the same lawfuls seeing you.
That is the stance of the Congress because as the official faction Hawk has to answer to the authorities in each house if we are caught doing something illegal or allow undesireables to dock at our bases. He does not inhibit us from doing illegal activities he just tells us to not get caught and to be careful.
Now an independent junker does not have to worry about such things. Hawk never said you could not pirate. He was explaining why the congress does not or looks down on it when we set up a deal and another junker spoils that deal by pirating them.
It is not oorp to draw a conclusion about how you got the ore. If he saw you tractor the ore as soon as the sairs blew up the trader/miner anyone can draw the conclusion that you are working with them. It would not be any different if a Hacker calls me to come pick up the loot from a trader he just vented into space. The difference lies in the fact that the congress waits to be called and does not sit next to the pirate while it is happening.
In the end, the Congress is trying to play both sides. Burning the candle from both ends. We want to have our cake and eat it too. We want the freedom to do what we want and not allow others to dictate to us how we are to live that is why we are junkers and for some similarities that is why the zoners are who they are.
The Congress wants to make credits just like everyone else, but we choose to do it with anyone who is willing to pay. That includes corps and the unlawfuls. When we haul ore for corps we do it not just for the credits but to strengthen our relationship with that corp and their respective house government as well.