True, not everyone behaves rationally all the time - but for the greater part, people tend to. Just because someone makes their screwdriver a little throat friendly you don't run around removing screwdrivers from everyone. Things seem to work out well there, on the whole. Military intervention seems unlikely to change anything.
There's nothing "magical" about obtaining infinite(from your perception) resources. There's no "somehow" either, it's pretty simple. We've just got to get it. It might take some time to unfold, but it's low specific effort and easily obtainable with a crowdfunding pool of current size. And to have any hope of actually building somewhere to inhabit then this, or something similar, will need to of been done. Sure that's no guarentee that everyone is going to be happy all the time, but it's certainly going to provide for an environment where there's no incentive for serious discontent. Those small minded enough to habour such ambitions will not be much threat, tactically. The scale of damages they can cause will be incredibly minor.
As for external threats - Why would they possibly want to try and take it when we'll just give it to them? Doesn't seem to make sense, there's too much effort involved. The key word in the opening statement would be "try". Lets look at the logistics of this one for a second. Lets paint a picture of a residential mass habitation station being attacked. If this was deployed sensibly(ie: what I'd do), there would be more than one in the near-earth orbital belt - several can occupy this space and be a lot closer(and potentially less hostile) than Earth, in the case of severe issues it can provide other places to go and or support that can arrive in less than an hour - Sensibly, these would have a variety of point defences. Each one not only able to cover itself, but the two either side. At least. There's a lovely array of non-lethal techniques that can be utilised to mitigate inbound ballistics projectiles, and as many if not more lethal with plenty of time to get it done. Particle or wave based energy based weapons are not on the cards just yet, but when they are they will be mitigated with equal ease. Lets just pretend it's not possible to mitigate such attacks, then look at the consequences of it succeeding - not to us, to them. Big chunks of station will likely survive re-entry and make a real mess of a lot of places. Think how much mass there will be. It'll wipe out the satellite networks, too. many smaller MMOD strike caused. Unlikely to be persued. To assume nine stations, each with a design spec capacity of 100,000 heads, with expansion capacity for another further 800,000 - to split our current population across(assuming everyone would want to "go" and no-one signs up and or breeds until about 2060 which is about the soonest I can wrangle construction to begin) then that's still at least 17k per station. Pretty much minimal. To think of more realistic numbers by that state in time, there's likely to be 500k+ per station. Lets say only 10% of that is prepared to stand at the airlock and cable-tie those that attempt to force entry, that's still 1700 people. Yes, I do know how big most militaries are. What percentage of them have recieved training making them suitable for a mission thus? How many troops you think they're going to get lifted at once? How many can fit through the airlock at once? Assuming we'd actually allow them to pressurise it, or didn't use the pressure in it to pop them off again and possibly fatally cripple their vessel. And how many of those are going to want to be in a waifer thin tin can drifting towards a well prepared adversary, who if they're feeling a little less civilised would ignore the "friendly" ways to prevent proximity and could centrafugally launch ten tonnes of unprocessed ore into their trajectory - or anything else abundant and worthless, or focus industrial cutting lasers on their fuel tanks, or re-direct the IR/microwave beams from our power transmission network into simply baking the occupants en-route, use the "tugs" that steal asteroids for mining to take them on a one-way trip to Sol - or any of a selection of more devious means to repurpose "innocent" hardware. Much risk, you'd be mad to try it - and as we'd just give them anything they'd want if only they'd ask for it, not much gain. With the way gravity works, delivery to doorstep(more sensible, defined drop zones) is actually trivial too. The logical thing is for them to sit put and wait for it to come to them, trying to take it would almost assuredly fail and even if it didn't wouldn't work out the way they hope. Zero effort, much gain vs much effort and assured failure. It's not a difficult equasion. Honestly, piracy would be more viable within a few generations of "independant" expansion, and that's just as easily countered by just giving them w/e they'd want.
Defence forces are not considered military forces, the differences are very important, especially in this instance. These are what enabled Japan to form defence forces when after WWII ended and they were no longer allowed to posess military forces. Typically, we should have no requirement for such things either - the closest purpose I can possibly envision being "search and rescue" and to be honest, response times to anywhere that's likely to be required are likely to make that a futile gesture.