At the point of filling the seats, as long as airlines inform the customer that they may be bumped. Then no harm is done. The passenger has significant notice that they may be bumped. It's one thing to buy a ticket with the understanding that you have purchased a ticket in hopes that another passenger won't show. But to purchase a ticket thinking that the plane isn't full is something totally different. By creating the assumption that there is enough space on the plane when the ticket is purchased creates the issue of deceptive practices.
Have no problem with that...but we also have to also realize that the Airlines are in the business of making money. And as we require changes in SOP, those changes could cause price increases or stricter requirements for ticket refunds.