I detest e-bikes on MTB trails for the same reason quads/ATVs/SxS on motorized trails. For whatever reason the lowered barrier of entry encourages something in people. It's not that I'm better or worse for being human powered but the point isn't about seeing how fast you can tame a trail but just the act of doing the taming. IOW the journey is the destination, or some such nonsense.
It seems to me in my narrow scope of interfaces is the e-MTB'er wants the rewards of a bicycle but without doing the work. They want narrow flowy trails and to be away from trucks and motorcycles, which is fine, but without all that tedious training and suffering that motors were invented to eliminate in the first place.
I love e-bikes for commuting, bar hopping, shopping. Awesome progression for the bicycle as utility. Absolutely something I see as technology benefiting humanity. A true case study in need vs. want and the effect on people and society. On one hand you have this thing that moves you efficiently and is less of a burden on resources that on the other hand feeds our inherent laziness and tendency to be jerks to each other.
And I know the irony of love/hate wrapping in this post. If the eMTB would be happy matching my climbing speed (local stud racer super climber passing me, much respect, lazy DH'er using assist, not) and just follow the accept etiquette of hike/bike/horse multi-use it wouldn't be the same. Yup, I was run off the trail by one...