I think your pediatrician is exactly right. The human body is an amazing thing . . . at least until we get old enough to ignore our body's cues and signals. When a toddler needs something (be it protein, grains, calcium, vitamin C, etc.), his body will crave it and he will eat it. When his little body tells him he needs protein, he will eat the protein that is offered. No normal, healthy toddler will EVER starve himself - it doesn't matter how stubborn or determined he might be.
Your son sounds like a food drama king! One of my two year old twin boys is a food drama king, too. I've always wanted to give my children as much exposure as possible to different kinds of food. (But I darn sure don't give my toddlers baby food!) With my picky twin, I literally have to present him with a new food at least ten to fifteen times before he will even TRY the darn stuff! I always make sure to provide one item I know he likes - though in a normal portion, not a huge one. Then I give him a small portion of the new food. He'll completely ignore it (or will toss it on the floor) at first but will watch all of us (including his twin brother, who will eat ANYTHING) with interest. Eventually, he'll take a taste. Usually he spits it right out and makes the "yucky" sounds, but I offer the item again at the next meal time. We'll go through that a few times before he decides it's actually pretty tasty. (He's discovered ham, steak, turkey, cauliflower, peas, and MANY other foods this way. He still believes broccoli was invented to poison him, though!)
Patience, repetition, and NO hot dogs or chicken nuggets in the house and NO forcing him (or even asking him) to try a new food is the way to go. Otherwise, if he's able to out-stubborn you when he's just a toddler, I'm really worried that you're going to end up with a super picky and unhealthy pre teen who will only eat cereal, pizza and chicken nuggets.