Comanchero: Not all archies are the uppity-up "purist" types. Yes, some are, and they are to be avoided like the plague. I heard a story about a guy metal detecting on an east coast beach. Not sure if it was county, state, or fed. A lady-archaeologist was walking along the beach and saw this guy. She goes up and gives him the riot act about how he is taking historic artificats that belong to ALL the public, not just him. The md'r tried to explain to the lady archie that he was only finding clad and current losses. The lady archie was stumped on that one! So she retracts, thinks a second, and retorts: "well, 100 yrs. from now they WILL be historic then, so you still shouldn't be doing this" Doh! You can't win with that type.
BUT there are cool archies I have run into, that have no problem with detecting, even in public parks and such. As long as you're not sneaking into their 2X2 test pits, or historical monuments, etc.... I have in fact gotten good site tips from these cool archies, and assisted them on their digs at times. So point is, you can't lump them all into the same class of purists. But I still tread softly around them, until I know which kind they are
As for the initial link that started this thread, that appears to be written by the type that .... if it were left up to them, no detectors would even be allowed in the most innocuous sandbox. And those types, I've heard, even try to dissuade private landowners from letting md'rs onto their land. Case in point: An archie group got wind of how some detecting clubs would "rent" a field, where known CW battles or camps were, in order to have a big group outing. Even though it was private, permission granted, etc... the archie group went public with their dim view of it. I guess this is because, let's face it, archaeologists do sometime do digs/studies on private land too, so taken to the 10th degree, you're "looting" and "taking items out of context" there too. But hopefully this purist attitude doesn't spread. I've only met a few of those types, but other archies can be cool about it, as long as you show them a good respect of artifacts and sites.