It is hurtful when folks you trust turn out to be untrustworthy. Mulder's poster in The X-Files comes to mind: "Trust No One"....
Truly, don't let anyone shake your confidence or your resolve to succeed at this. You're absolutely on the right track in doing your own research and the advice you have received about finding the right person to take lessons from and to get training assistance from is right on target. However, that should ALWAYS go hand in hand with doing your own research and thinking for yourself along the way.
WhatEVER you do, DON'T QUIT!!! Sooner or later you'll wind up with a relationship with your horse that will be priceless beyond description. It'll all be worth it!
If the folks around you at the barn are "dragging you down" then that just means you need a different group of folks around you...
Now I hope things turn up and start getting better right away!
I'd just like to address that reading about how to train a horse or any kind of research is a very smart move and it was rude of those people to kill your confidence in yourself. You are very smart, and don't let those people affect you. I'm currently dealing with the same thing, it's hard to not be hurt when someone you trusted or held in such high regard turns out to be a bully of sorts.
If you truly want this horse, there are ways to turn it into the horse of your dreams, but it'll cost you in training expenses or riding lessons from someone experienced. I have to tell you from experience, though, I find it is worth it.
I hope things work out for you, you are amazing.. don't let anyone tell you less and don't think any less of yourself!