I've been around baby forums for a loooooooooonnnnnnnggg time, and my opinion of BFing encouragement sites like KellyMon is that on all occassions they will say the same thing...
"Your Breastmilk is sufficient..."
"My baby is dehydrated..?"
"Your Breastmilk is sufficient..."
"My baby is very hot in a heat wave, should I give him some water..?
"Your Breastmilk is sufficient..."
My baby has conjunctivitus..
"Your Breastmilk is sufficient..."
My baby has exzema
"Your Breastmilk is sufficient..."
My baby has a black eye
"Your Breastmilk is sufficient..."
My baby was knocked over by the dog and has a broken arm...
"Your Breastmilk is sufficient..."
These webistes are neither medical authorities or unbiased. They are there to encourage people to breastfeed or to note the benefits of breastfeeding.
You took your baby to a medical professional, he determined that your baby is slightly dehydrated and offered a solution. If he was seriously dehydrated he'd be in hospital on a drip, so its a mild situation.
If he hadn't offered any solution to this rather than "just feed him more", would you be here saying "I am furious, I was told to feed him more....does the Emergancy Dr think I'm with-holding bm from my baby, I'd never deny him a feed....he should listen to me as a mother..."...
Look, you are stressed because your baby is ill. You being stressed and upset because your baby is ill does not mean everyone else is wrong. The Dr offered a solution to your baby's problem, thats all.