So, based on that definition, it is true that Bitcoin is not a fiat currency because it is not given value by law or government. However, although it technically does not have a centralized issuing authority that can arbitrarily create Bitcoins, Satoshi Nakamoto did hard code a creation rate for Bitcoin. In a sense, he is the original issuing authority. The only difference between Bitcoin and fiat currencies, when it comes to currency manipulation, is that Nakamoto committed early on to a specific plan for issuing currency. The government (or the Fed) not only does not make that commitment, but it is unable to make such a strong, unbreakable commitment, although it verbally makes similar commitments all the time.
What is a law or a government in any case? Bitcoin is created by rules. The rules are embedded in a program instead of a law-book. The governed users opt in by using the software rather than by living in some geography. The rules are enforced by being mathematically unbreakable rather than with courts and prisons. These factors alone shouldn't be especially significant, other than that they make Bitcoin more just and efficient.
In fact, with respect to money creation there are not a lot of set rules. The main problem is keeping supply matched with demand. From a governmental standpoint demand is usually enforced (at the very least by forcing taxes to be paid in your currency).
In other words, your criticism would be considered a design feature by many economists. Some even considered adding a fee (demurrage) instead of facilitating inflation, encouraging you to use whatever money you had. This would be akin to a 1% asset tax instead of an income tax.
There is also a voting mechanism that can change the Bitcoin protocol, the NSA for one probably has enough computing power and bandwidth to flat out 'take over' the network and give themselves arbitrary bitcoin amounts.
PS: Voting is a basic problem with all network based protocols. If enough machines say this is what happened then that's what happened.
We can argue about whether or not that is a good thing, but let's at least be clear about what we're talking about. Using definitions of words that are different from what everyone else uses is not the way to communicate your ideas to other people, let alone convince them that you're right.