I think this has gone to an extreme.....
Where I live, the County does not have a requirement for a permit to MD. However, if it is posted that MD'ing is not allowed, we must follow that rule. On the other hand, public areas, parks, BLM, and Non historic sites are ok. In the same breath, and often confusing, is the verbiage used in the Regulations of the National Forests about MDing. Simply stated it is allowed, followed by the usual; not to disturb, disrupt, dig etc the natural habitat. Followed by a statement of "the use of Metal Detecting to find coins", in which it states that most coins are found in relative depth of 4-6", which in this case is allowed.
The rules are so contradictory that it makes it difficult to understand or make sense of anything without a JD.
Then we go even further to "ask" permission (on something that is already stated that it is ok) from someone who chances are does not know the first thing about the hobby and will not give permission out of fear.
I detect openly and honestly. I take great pride in retrieval. If I can retrieve without cutting a plug, I will do so. If I need to cut, I use a drop cloth for the bottom dirt, retrieve the object, and replace the plug and you can't tell that I was there.
You can use all kinds of examples of "Turf" abuse that you want...golfers, aerators, Quads, Cleats, Spikes, Bikes etc. the bottom line, take pride in what you do, and respect the property you are on.