Judging by the comments of the pro-sled crowd on this topic, the only place that sleds aren't allowed (that is the correct spelling, not "aloud" for those on both sides who don't know better) is in wilderness areas. This argument is supported by the repeated statement that
They are called wilderness areas. Areas where no motorized travel is permitted
. Taking your logic to the next step, this means that motorized vehicles should be allowed anywhere except in wilderness areas. Does this mean that you believe that in the summer, ATVs and 4X4s should be granted access to any part of the national forest, irregardless of the lack of trails and roads, including places that are currently untouched by any motorized impacts? If so, do you then support the idea that roads and trails should be built into said areas so that these motorized users can access these areas? Since the Summits of Grey's and Torrey's peaks (2 of Colorado's 14er's) are not in a wilderness area, should we allow dirtbikes to rip their way to the top? Should we create 10' wide trail up there in the winter for snowmobiles? If I complained about hill-climbing motocrossers ripping up the tundra and spitting rocks, dirt, dead Pikas and dust in my face on the trail at 14,000 feet, would you tell me to go hike in the wilderness area if I don't like it?
Just because a piece of national forest land is not "wilderness" doesn't mean that sleds should be there. The very fact that you can go anywhere you chose on the snowpack, and often do despite those areas being wilderness, means that your activities can have serious negative impacts to the flora and fuana of the areas that you ride.
There are tons of places for snowmobilers to ride that already have heavy motorized impacts, are still fun and challenging, and don't lead to excessive user conflicts between skiers and sledders. Think about it!
And yes, to those that will feel obligated to berate and criticize my comments, I've spent plenty of time on a sled. I also spend more time skiing in the backcountry, and I've seen asshole slednecks and asshole skiers but mostly I've seen good people that just love being outside irregardless of their choice of sport.