As far as the story with the 13th company goes, they are all loyalist
SW and the one thing that prevents them from falling to chaos besides their undying loyalty to Russ is the Cannis Helix (or wulfen gene) that all
SW have. When a wolf embraces the wulfen inside himself it helps protect him from the powers of chaos and making him an effective weapon against it.
Now the =][= trying to declare the
SW as traitors and/or heretics. One of the reasons is that they wont do what they are told to do so that puts them on the

list with the munitorium and the High lords of Terra, in fact in the codex one of the =][='s investigators says the sure way to get a
SW to do something is to tell him not to do it!!

Another reason for the investigation is that they don't like the slight mutations that all
SW have with their fangs. So they get all duurrtarded about it and try to oust them, then half-way through they realize that they cant afford to loose such stalwart warriors and back off.
The
SW are very much like old Viking and Norse warriors, fiercely loyal, love to fight and drink, and will bash in heads if anyone questions any of those core values!!!!!

*Slams down an emptied Stein of Mead and lets out a loud belch for Russ and all Space Wolves*
Later
Gareth