Focus instead on finding and learning with other open-minded people.
Trying to identify bad faith arguments is lose lose lose.
If you successfully identify a grifter, what has changed? You can judge them even more harshly for their cynicism, but isn't it enough to judge them for their harmful words and actions?
If you successfully identify a useful idiot, what has changed? You can judge them slightly less for their harmful words and actions. You can consider them redeemable and attempt to change their mind. Is that a good use of your energy?
If you fail to determine for certain whether someone is a grifter or a useful idiot—and uncertainty is the most common outcome—you've simply wasted your time.