Yeah, I don't know why you guys are getting your panties in a bunch about OP being or not being a troll. S/He seems fine to me.
Now, as for carbon being called "fragile," it is and it isn't. Carbon fiber is one of the strongest materials out there. Far stronger than steel and aluminum. However, when carbon fiber fails, it fails in disastrous ways. Say, for instance, you hit a steel frame with a hammer. Depending on how hard you hit it, it will be in various states of dented, bent, or or possibly broken apart. If you do the same to a carbon frame, it will begin to crack and shatter. Think of it like wood, since both carbon fiber and wood are composite materials. When wood fails, it splinters, cracks, and shatters. Carbon is the same way. So a carbon bike might not be good for a beginner because you might not take proper care of it. A steel frame you can kind of throw around and not worry about it too much because a slightly bent tube a won't be the end of the world. An unattended crack in a carbon frame will eventually result in the whole frame being compromised. There are easy ways to repair cracks in carbon fiber though.
Carbon is a great material for building bikes since it is very lightweight, stiff, and yet offers a very smooth ride. It's also much more expensive. You usually can't get a carbon bike for less than $1500, which is another discouraging factor for beginners.
As for getting the fit right, each person is different. When you test ride bikes, the shop will set you up on a bike that fits you well in a neutral position, just so you can get a general feel of it. If you buy it, you ride if for a few weeks and let everything settle in (gears, cables, etc.). During those few weeks after you buy a bike, the shop (good ones, at least) will do various adjustments on your bike to make sure everything is still good. That usually includes cable tightening, derailleur adjustments, and fit adjustments.
Getting a "pro fit" is kind of something you do after you've been riding a while, know what you want, and want to have a top-notch mechanic fit you in a way that best suits your riding style. You don't even know what your riding style is yet and what's comfortable for you, so a "pro fit" would probably just be a glorified version of the fitting you got when you first hopped on the bike for a test ride. Getting professionally fit has its place, but it might not be worth it for you at this point.