There is also animosity between upright and 'bent riders. Some of it (I'm told, no first-hand experience) can get pretty nasty.

Humph!

If it is moved forward by human power, I'm good with it. Especially if the human looks to be having a good time.

Carbon racers, MTBs, hand cycles, 'bents of any discription (and they are many and varied), 2, 3 or 4 wheels, tandems, sociables (side by side riders), whatever. I've seen 'em all at least once on local bike paths. They all made me smile. I've even lusted after a few. They're all good.