It's just such an arbitrary distinction. They are separate legal entities, but CCFC are owned by Sisu.
Really don't want to get into this, but as I can't resist a tedious argument on semantics, here we go:
Sisu's offices aren't Sisu, they are something that's owned by Sisu. Yet you suggested (IIRC) that gluing the locks at their offices would be a justified protest (as an example, I know you weren't suggesting we do it). But that would be targeting Sisu's property, not Sisu. Similarly attacking their investors isn't Sisu, it's their relationships.
A company is a legal construct, not an actual physical thing. Any protest will inevitably not be "attacking Sisu" but something they own, just like CCFC. Which is why the whole distinction is pointless.
Standard disclaimer that I don't support protests that harm what's going on on the pitch or lead to points deductions, but because I think it loses us the moral high ground rather than because of some pedantic distinction between the two entities. It is my belief that Sisu are fucking things up enough on the pitch to give us a valid complaint, adding to that ourselves muddies those waters.