Again, you're analyzing what Galileo did with the benefit of hindsight. With hindsight, we know who was using the telescope correctly and who wasn't. At the time, you had a complex set of rather fuzzy observations made using a poorly understood instrument, and some of these observations were in conflict with arguably more reliable observations. Feyerabend is pointing out that Galileo wasn't right because he was more scientific and more rational than his critics. In that sense, his decisions to accept certain bits of evidence and ignore others (e.g. the apparently obvious fact that the Earth is not in motion) were arbitrary. That is, these decisions did not follow from (and in fact sometimes went against) the scientific method as it is typically enunciated. With hindsight, we can offer a post-hoc rational reconstruction of each decision, but that can't be taken seriously as an account of what Galileo was actually doing. So yes, the scientific method is a myth if understood as a set of guidelines the following of which has been a major cause of scientific progress.