If someone from either side is just trying to save fresh tracks and privacy, in easily accessible and navigable terrain, with easy parking.....good luck. Actually, they already have that for skiers everywhere....they're called "ski hills." Better get there early on a good snow day, just like sledders going to popular easy-access sled spots.
If you desire a more backcountry experience.....well, as someone who does a range of winter activities.....one must really suck at skiing, touring and snowshoeing if he/she wants to use the same areas as snowmobiles. I believe that if both groups are allowed to share the roads that the rest will sort itself out. Ya everyone wants fresh tracks all the time....and you CAN have that on skis or a sled, but only if you're willing to work for it. How about all the touring that's easily accessed from ski resorts that sleds aren't allowed anywhere near? Huge tenures for cat/heli skiing with the same sled restrictions? Terrain not easily accessed by sleds? Plenty of places to go skiing with ZERO chances of seeing a sled.
To suggest that there isn't enough land out there for both to co-exist is asinine. To think that co-existing on public land means that one group must be segregated to a certain area is dumb IMO. However, if that's the only way, at least make sure the areas make sense geographically. There is a ton of non-motorized area set aside for skiers that they can't even get to with days of touring.....what's the logic in that?
So rant portion over....yes, sledders need to pump their groups, or coalitions, or whatever to new levels. There are more people sledding mountains that ever, and snowmobile clubs have not kept up, or even sustained original levels it seems.
IMO, the defense in this matter, is actually offence. Most snow clubs are just cruising along with whatever they started with (area and members). They need to be actively pursuing new members (social media should play a big and relatively user friendly medium), and new areas. Clubs should be spending as much or more time applying for new tenure, as defending against movements such as this. By the time that comes along, the "other side" already has a great sounding game plan put together (doesn't matter if it makes sense to you or not), and snow clubs are on their heels.
Since the non-motor side is not willing to share when they get access, the snow clubs need to persue more exclusive tenures to operate on. "Exclusive" will likely mean joint, as I doubt you'll be able to keep non-motor people off any public land, but joint is fine as long as it's the snow club sharing it, not vice versa. Now that's easy to say and I'm no better than anyone else, but that's my 2 cents.
The enviro side mentioned is just to pull on the heartstrings of the political side....it works tho (for reasons beyond my understanding), and that's always a tough egg to crack for sledders. Ski with a helicopter and you're an upstanding environmentalist....snowmobile and you're a mini Exxon-Valdez. Ski hills are everywhere, they're not environmentally friendly in any way, they all on what once was public land, and most of everyone drives their vehicles to/from individually to park in massive parking lots that have been logged, slashed, paved, etc. Doesn't have to make sense.....you just have to know that's what you're up against.
I will take environmental $h1t from the guys/gals who bust it right from the road for hours on end just to do 1 or 2 runs....there are some of those guys around here, and they are the ONLY people I consider truly "low impact." Most people are not that athletic, and that's what ski hills are for...