When my boy was really little he was pretty defensive towards me too when it was time for any kind of interaction. He even nipped me a couple times. It was sort of cute lol. Such big attitudes in tiny packages!
If he's new to your home I'd suggest giving him a couple weeks with little handling to really settle in and keep any noise level down to minimize any stress he might be experiencing.
These are other methods I used on my boy as well...
Put a worn t-shirt in his tank for him to acquaint himself with your scent as you are both new to each other.
Practice laying your hand on the floor of his enclosure from opposite ends of where he is and slowly inch your way to him so that your hand is less threatening to scoop him up. This may take some time for the little one to not perceive you as a threat regardless. It did for my dude lol. This does help though because he/she may feel threatened if you reach down to grab them from above.
When my boy was really aggro and gaping at me, I would slip a little piece of greens in his mouth and just kept feeding him bite sized pieces until he'd calm down or go to hide under his hide. I let him be if he was hiding. I wanted him to feel safe in his enclosure so I never picked his hide up when he was in it.
Spend time around his tank. I would do research in the same room as my dragons tank and read out loud for him to get used to my voice from a distance. It was quite funny cuz he'd come to the very front of his tank and stare at me for minutes at a time. He was so small all I could see was his tiny head above the trim of the tank checking me out while I was reading. :lol:
I did these things for up to 2 months before my boy settled down and accepted me. Hard to remember because it's been so long now. He's 4 years old now and very friendly. My previous dragon was a sweetheart from the get go. The time it takes will vary. Just stay patient with your little one and they will come around. =]