How would someone “boycott” or refuse to pay a fee and still get booked on a flight? I don’t think more than a handful of frequent flyers would, in protest, only book their flight at the basic economy fare. Or is the proposal that, whatever fare class you choose to fly, you don’t choose a seat that has a fee associated with it?

With certain fares and certain membership levels, you can have any seat you want, so if you’re of the “privileged” class, there’s really no way to boycott. The way the industry works these days, what one airline does, the others do. If, for example, a large number of people stopped flying on United and booked on another airline (and paid the seat fees there as long as they’re willing), perhaps United might take to the suggestion that “I’d fly with you if I didn’t have to pay extra for an aisle seat” and the rest of the airlines would follow. But for many, I feel that giving up their privileges on one airline for a possible greater good might be too much of an obstacle.

Well I guess that they can charge for these if they're upfront about it. But UA basically threatens the passenger and tries to convince them not to use the fare. I'm a Million miler w/UA and find this disgusting. Here's my message to UA:
Your sales tactics for basic economy are both ridiculous and threatening. Other low-cost airlines, such as Southwest Airlines, give two free bags and other amenities, particularly treating customers like human beings. I think that United airlines are idiots for how they market their basic economy ticket. I have taken American and Delta on the same fare and they are much more amenable. Since I am a Premier gold passenger with United, I don’t have to worry about some of these Draconian features; If you really don’t want passengers to use this why don’t you simply eliminate it and become competitive with other airlines?