Some who are user/broadband ISP's (not say, tier-1 and
tier-2's who would be against it: "don't be the
Internet's Firewall") are blocking ports such as 139 and
445 for a long time now, successfully preventing many of
their users from becoming infected. This is also an
excellent first step for responding to relevant outbreaks
and halting their progress.
Philosophy aside, it works. It stops infections. Period.
Back to the philosophy, there are some other solutions as
well. Plus, should this even be done?