California has a program to help private landowners thin crowded forests to reduce fuel loading and improve timber growth. The environmentalists I know all favor it, and many are actively participating either as landowners or as workers. The US Forest Service also has a fuel reduction program, which some, but not all, environmentalists support. Many environmentalists would like to see more effort in this area, and allow cutting of commercial sized tree to help finance it. The facts are not as simple as your post suggests.