Norton is terrible for LANs.
Spyware applications are not 'borderline viruses". The vast majority of any kind of spyware or adware is installed by users when they install other software, or visit dubious web sites. On a LAN it's up to the network administrator to prevent this, sure, but that has nothing at all to do with AV software.
AV software doesn't stop koala bears from pooing in your CD-ROM either, but nobody is going to claim that's a reason to not use them.
If it works best for you to do it by hand then that's great, but I don't see any justification for claiming your way is super and everyone else is just stupid.
At least we can agree most of the problems PCs face are due to user ignorance, or the unwillingness of some users to co-operate with network admins?