As far as I know provided owners have paid their relevant taxes and duties, we all have equal opportunity to access and use public highways. The same is true of owners of campervans, as it is of caravan owners and indeed all road users.
In certain places there are legal rites to wild camp, and in urban areas there are local by-laws that can define what vehicles may use certain roads, and the same for parking restrictions. This means that some vehicle types may experience more of less restrictions such as no HGV's or Pedestrians have Priority, Taxis only or Bus lanes, permit holders only etc etc.
Some people based on what vehicle they have may be able to do things that you can't, and vice versa. Most of these restrictive limits are applied to larger or commercial vehicles, and private cars usually have greater freedoms than most other classes of vehicle.
Most of the restrictions are applied by local authorities rather than government. So if you think you have a legitimate complaint about a local issue then take it up with the relevant authority,
Not all motorhome and camper vans cost big bucks, some have been home conversions done on a shoe string budget becasue the owners don't have as much spare cash as well heeled caravan owners, and they cant afford the cost of some sites, or perhaps they don't like the site, so if wild camping is allowed in your area, they are not falling foul of any laws or moral rights.
As Beachball constantly reminds to each their own.