Two points come to mind.
1. He's exceedingly jealous of you and your bike.
2. He feels inferior because of your engine size and your stature.
Be a good friend and don't change.
...and if he's that small; maybe he should stick with the 600.
Well here is the background story.
I have been friends with this guy for years. We were both into cars, and i always was helping him out. I would give him advise, then he would go do something totally diffent. A couple years pass... i end up with a 9 second car, and his is still stock... he kept changing his mind and selling parts he bought, and never got around to put them on. He isn't very mechanially inclined, so he had to wait untill someone would help him.
About 5 weeks ago i went and bought an 04 R1. He saw it and loved it, so he went and bought a bike too. He was going to get a brand new bike, but i talked him into getting a little bit older bike, because these were basically going to be our "learner" bikes. I also didn't want him to get hurt, because he tries to ride/drive beyond his ability... and has ran his car off the road for some (frankly stupid) reasons. He shows up with a 2004 GSXR 600 a few days later. Me and him went riding every day, starting out on backroads, working our way up to the highway and interstate... etc. Within the first week of riding, he had already dropped his bike twice.
A couple weeks pass and i decide im just too big for the R1 (it killed my back and wrists). I decide i want a Busa after sitting on one, so i go trade in my R1 on my 2008 Busa.
Now that i have the Busa, he is afraid everyone is going to say he has a "baby" bike because its only a 600. We have been talkin about takin a motorcycle trip, but he doesn't even want to go untill he gets a bigger bike because he is afraid people will make fun of him for having a 600.
This guys is one of the nicest people you will ever meet, but he is just an air head. He only wants a Ducati because he wants "something no one else has". He didn't know anything about them, he thought i was lieing to him when i told him they were a twin cylinder motor.
He doesn't have money to burn, but he makes decent money. If he wanted a 20k bike, he could have it. I just know he is buying it for the wrong reasons, and he would be just as (if not more) happy with a GSXR 1000.
I dont want to turn this into a pissing match with him. We are good friends and we started this to have fun. He thinks that part of the reason i bought the busa, was to "1 up" him. Not the case... i just wasn't comfortable on the R1.
You ever have a friend that you try to look out for, because it seems like every decision they make is a bad one, and you want to try and help them if possible? That exactly how it is with him.