Depends on the hubber and hub content.
I wrote quite a few scam-busting hubs, which put me up against quite a few people who promote suspicious schemes, and wrote hubs about them. They usually deal with "income opportunities"
Those people do NOT respond well to criticism. The only thing you can do to those people is flag them.
For people who may actually be interested in amending their hub, simply provide citation to the facts as you found them, and see how they react. If they change their hub and thank you, great!
If they just delete your comment / deny your comment (you can see that in your activity log) then you may want to put up a link in RBUTR.com, which is like global webpage comment system.