My view:
Pinning is NOT fly fishing. The definition of fly fishing is using the weight of the line to cast, rather than the weight of the lure. So as long as you call it FFO, I'd be against it.
That said, from a conservation standpoint, I'd also be just fine with turning all FFO areas into ALO. And pinning and spinning gear would be allowed so long as they use artificials.
In other words, I think most special regs should be based on conservation rather than attitude. The goal is that a fish survives getting caught, so that it can be caught again. And I don't really think the rod, reel, and line have much to do with fish survival %. Whether or not the angler harvests the fish, and the offering at the end of the line, both do have a notable effect.
The downfall of pinning is that many take more space than anglers of other types. Hence, they can be particularly troublesome in other ways, namely, under very crowded conditions. If you wanted to create special regs intended for a very different goal, then I could understand "no pinners". It would be implemented on very crowded streams (or even at certain dates), and the goal would be to allow more fishermen to fish smaller areas with less trouble between them. As a good example, the mouth of Walnut Creek in Erie would be a prime place for a "no pinner" rule basically all fall. Opening day on urban streams as well.
Other than that, live and let live.
They have various concerns, but the most frequently mentioned are litter and privacy, and if center pinning did not generate any greater amounts of litter than fly fishing or significantly more foot traffic I doubt that the landowners would be interested.
That bothers me a bit. Especially the litter part. Whether or not an angler litters has everything to do with their behavior, and nothing at all to do with their choice of tackle. There may be a correlation, but not causation, they aren't really related. Many spin/bait guys don't litter, and many fly fishermen do.
As for foot traffic, aside from the first few weeks of the season, I'd guess that any special regulation increases it rather than decreases it.