I believe the waters are a bit muddled here, and people are talking like there's one group out there doing one thing.
13th Legion has announced a blockade of the CG, because they don't believe Halsey is being truthful about it being done to establish a rehabilitation centre for war refugees. This is based in a large part on the materials being asked for if I understand it correctly. So, they are completely blocking the CG and will try to refuse anyone to deliver materials to the station. They will also announce this prior to interdicting anyone, giving everybody a choice to either push through or leave of their own will.
The CODE however, are straight up pirates. They will interdict you, demand a part of your haul, and if you comply they will let you continue. Some will even escort you to the station afterwards.
Other groups out there will however interdict and kill you just because they can. If they do this, they should not belong to either of the groups above. From what I have seen, it seems that most other groups try to fight the 13th and will focus on this. If no member of the 13th is in the instance, some of them may however turn to their usual antics of blowing up traders for lulz. Nothing new.
Hope that clears it up a bit.
And I am all for people joining up and fighting back. I think the other side would like that as well. May I suggest talking to AA (no, not the 12-steppers!) and see if they have anything going on there where you can help. Or just get a few guys together and run escort missions.
PS: And for those confused about the responses the OP got; read his post again slowly. It does not read "Let's get together and have some fun".