The Fallacy Fallacy

The fallacy of concluding that because the logic someone used to reach a conclusion is broken, then the conclusion is itself wrong. For example, if Tom concludes that Rover is a dog because dogs are furry and Rover is furry, then it might just be that Rover is in fact a dog (rather than a squirrel or cat, which are also furry) despite Tom's bad logic.

Or, Paul argues that the sun orbits the Earth rather than the other way around. Rather than refute Paul with real evidence, Lucas just rolls his eyes and goes, "whatever; you're just a hick from Tennessee; you'd believe any crackpot thing you heard on the Internet." This is an attack on the source, but it doesn't change the fact that Paul is wrong. And then Paul could commit this fallacy himself by pointing out that Lucas is using the Fallacy Fallacy, so therefore he must be right!