It's usually better to look for the organization who is delegated a particular block by consulting the appropriate registry - in this case ARIN.
I'd send the complaint to:
TechName: Domain Administrator, Administrator
OrgAbuseName: Abuse Complaints
as well as possibly to postmaster / abuse at perf.bc.ca (the organization to which the smaller block is registered to. However, note that unless there is a threat of violence in the post, the ISP will most likely not take action (and in any event, they will not be able to give you information about the user, although they might kick them off).