The columnist doesn’t question the truth of the analysts’ premises that boomers will start planning for retirement, thus saving more and consuming less. The columnist just makes a different prediction based on these premises.

The columnist never suggests that the analysts’ argument is wrong because it’s self-serving. Sure, if the analysts were correct, they would “stand to gain,” but that doesn’t mean that they benefit from just making the argument.

The columnist’s alternative conclusion, that boomers will probably not invest heavily in stocks, is indeed drawn from the analysts’ same premises. These premises are that boomers will soon start retirement planning, leading them to consume less and save more.

The columnist doesn’t agree that the analysts are basically right. The columnist’s claims that stock prices will stay low and boomers will invest elsewhere are totally opposed to the analysts’ conclusion that boomers’ investment in stocks will create ongoing gains.

The columnist simply doesn’t argue in favor of the analysts’ conclusion; nor do the two use different evidence. In fact, the columnist uses the same body of evidence to argue against the analysts’ conclusion.