You can argue that Wicca is an Agrarian based religion, but it is most certainly not a nature religion. The wheel of the year is based off of English farming stuff. It is also a romanticized view of the Manor born. The Lord and Lady, are the spiritual Lord and Lady of the manor.
You have 3 harvest festivals. You have the equinoxes and the solstices. You have the spring planting and fertility festivals. All these point to an Agrarian root. The Farmers Almanac would not go amiss, to be used in planning rituals.
The people who argue this is a Nature religion, don't have much experience with nature. They are city or suburbanites. I dare say, they don't have much experience with even gardening. They have this romanticized, idealized view of nature. Nature that they experience in tended city parks, where most of the big bad predators have already been killed off.
Having rituals under the full moon, naked or no, does not make you closer to nature. It makes you camping religiously. The night does not hold terror for you that it does for those who really understand what nature is. The time of plenty(harvest) and lean(winter and early spring) does not hold the same meaning to them as it does to those who live the Agrarian life.(see third world Africa sometime, or other poverty stricken areas).
If Wicca were a nature religion, than the adherents wouldn't pooh pooh people in other countries for being superstitious about things out of their control. They would understand that a cow loosing it's milk, could spell death, or disease or hardship to someone, not an inconvenience. They would understand that a bad harvest could wipe out a family. They would understand the lack of power that these people have, and the uncertainty that they live with. That btw breeds illogical superstitions, which science and reason combat far more effectively than annoying letter writing campaigns telling people how bad they are.
Nature isn't nice. It has a strong predator and prey aspect to it. If Wicca were the nature religion that many purport, than cursing wouldn't be such an issue. Neither would animal sacrifice. Dont' be around negative people, would not be such an issue, because passivism would not be encouraged.
So don't mind me, when I snort, when I hear that asinine phrase. I hug trees too. I garden as well, can't veggie garden worth a damn, but I garden. But when I was Wiccan I did not worship in a nature religion. Turning to a more Polytheistic roots, it still isn't a nature religion.