The one crackpot I interacted most strongly did have experimental results, and trumpeted them loudly. The experiment turned out to be a notoriously finnicky one (not quite down to Millikan experiment territory) done in slipshod fashion. This was utterly predictable, given purely theoretical considerations and examination of his style, even before it came to the observations - his theory contradicted, say, the existence of comets.

Experiments can be wrong. Maybe even most attempts at experiments are wrong. What makes a scientist a scientist instead of a crackpot is the debugging and validation. Trying to exclude every way the results might not mean what it seems like they mean - not just doing control-experiment comparison and saying you've done your duty.

Crackpot experiments, lacking these extra checks, are worthless.