To me it is telling womin that their bodies are no good at preparing to birth their babies and they need outside help. To me this device implies that a womuns body is inadequate and may reduce a womuns confidence in her body to birth without assistance.
I'm pretty sure my body is capable of doing a backflip too.. but I certainly wouldn't attempt it without a bit of practice or warming up! I think if anything, at the very least, using an epi-no or doing perineal massage lets you feel like you're doing something to help prepare your body for one part of the birth process.

It's the same with pelvic floor exercises that everyone insists on.. is this because we don't trust our bodies to know what to do after birth?

I don't think it reduces confidence in our body's ability, I think it could boost confidence..coz when you use it.. you think.. hey.. this is pretty easy! And it's such a gradual process getting up to "birthing" size.

I really don't see the harm in either perineal massage or epi-no when done in a balanced way.