There are a few takes on this:
- If someone's just bullshitting you straight up, and you can find multiple instances of this by examining the more straightforward parts of their statements, then you can choose this route. This also often applies where there is no there there --- where an "argument" is simply an endless firehose of muck, as with the Qanon case.
- If the core is solid, and your goal is gaining knowledge rather than Winning Imaginary Internet Points (or playing at more substantive rhetorical games, of which there are in fact many) ... then you've won by learning something.
- If the core proves difficult to untangle or validate --- pointing this out is a valid criticism as you're putting additional valid burden of proof on the party arguing that case. Without substantiating their points, the argument is based on confusion, uncertainty, or ignorance rather than empirical merits.
- In many ways, empiricism is a Steelman argument of the form "evidence trumps theory". If there's some theoretical argument and you can show that the evidence clearly contradicts it ... I'd argue that's a form of steelmanning. Of course in reality such evidence may be tremendously hard to obtain, or not clearly decisive, or require extensive interpretation to judge.
- There are arguments which come down to statements of values. As was pointed out on the Ezra Klein podcast earlier this year, it's really hard to definitively argue for the superiority of one set of value judgements over another (though not necessarily impossible). You can point out that this is the nature of the disagreement, however. In the sense of steelmanning, this would be a case of pointing out begging the question in its correct sense --- if you presume that your argument's conclusion is a superior value, then you cannot invoke that assumption to prove the conclusion as the argument is the conclusion. I'd had a recent discussion of tenant vs. landlord rights on HN where this seemed to be the case. You can state that property rights are important, but if you're using the assumption to prove that property rights are superior to tenancy rights ... you don't have a logically sound argument.