and bitcoin is a"Clear and Present danger for them" they are not stupid.
You can't "kill" bitcoin - there is nothing to kill, no central authority and it's done like that by design and on purpose - a lot has been learned from how Internet works as it was developed as a technology which must survive nuclear bomb attack at a point.
US passed a bill which allows existence of virtual currencies: http://www.fincen.gov/statutes_regs/guidance/html/FIN-2013-G001.html
To effectively kill bitcoin you have to shutdown entire Internet (or at least large portion of it), that is by design not possible (see above). If it would happen anyway well, buy rather guns than Bitcoins
You can sort of try to kill Bitcoin by making it illegal - that is not happening (see fincen.gov above), though it would probably won't be too effective. So to save making fools out of them selves they tried different approach. Did war on drugs, war on terror, war on piracy, war on ... actually bring any results? I don't think so.
Btw. Here is example of the fool who clearly does not have a clue how things work nowadays: http://www.capitalfreepress.com/3181-senators-inadvertently-send-thousands-customers-silk-road/
Plus as big money are starting to pour in (search the forums for "fund") they would probably won't bee too happy about it and no more support for next elections
Yes you are correct, if there is no unexpected event (World War 3) I strongly believe in these valuations and they will eventually happen as masses adopt Bitcoin.
Decentralized in a way that each computer can act as a bank as it holds the whole database of all transactions - yes at this point it is in volume of Gigabytes (GB). I have no idea what your technical skills are, but take it on faith that it's a lot of data.
You can stop them by learning programming skills . But it's not really necessary - there are already plenty people taking care if it. I would say - when you buy an airplane ticket - do you understand how it works before you get in the airplane? Or how about Microsoft Windows? The general consensus is that if the software is opensourced (which bitcoin is) it is usually way more secure then the proprietary (closed) source.
You are welcomed, hope it helped.