Australians were forced to surrender their guns. Now they are at the mercy of whatever form of tyranny develops in their country. Without guns, you have no voice against those who possess guns. The US Revolution began when the Brits tried to seize weapons. Lots of lip flapping up until that time about taxes and monarchies and rights, but when they began to move against the armories, the battle was engaged. The US would have lost the Revolution if another year without action had passed. No guns and powder would have been available.
And sure the more aggressive groups will be targeted first. Especially young people (whom old people envy) will be shown defying the system in order to get conservatives and moderates onboard. But once the Greenpeace people are declared traitors, what about school teachers, gardeners, etc? If you allow a govt to set an abusive precedent, it will be broadened. You can bank on it.