Most if not all the so called MTBR trails in my area started out as game trails, with the dirt bikers and the horse people helping out. Flying around low level like I do, (in the plane, not going fast on the bike) I see trails all the time, everywhere, they are by and large game trails.
Being on the same trail, while riding the same way and speed, not making any noise, not going any faster other then not stopping to gasp for air, I don't see where the MTBR get off claiming these historically "multi use" trails are now their own. And....at least around here, they don't. I can see the hikers getting their panties in a wad when mountain bikes first came along, then got more or less accepted. The more populated parts of the country, and Idaho ain't one, I guess have a lot more pressure on their trails and less public lands, and if the trails were started by the MTBR's and not by others, I say they may have an argument. Duh..... When I come up behind a MTBR on a otherwise multi use trail I won't pass them, I'll take a break and let them get ahead, sure I could sprint past them and (maybe) kick dirt in their faces and if I did, I'd expect to be call an a hole. But with what seems to be the demographic of the e bikes users, a lot of old guys, I'd like to think we got that out of our system long ago, I'm just happy to be out there pedaling my ass off while getting a small boost when needed. If I was in my 20's I'd worry more about getting hassled by the MTBR's the same age, but being one of the oldest out there so far it has been no issue whatsoever. They cut me some slack I guess.
In a few years, this will all have been thrashed out, probably by the MTBR's being outnumbered by the e bikers.