Libya and Syria are probably good examples of this not being the case. Libya had the benefit of NATO coming to the aid of the rebellion and stopping the airstrikes, Syria also had outside involvement. When a government goes to war with it's civilians other nations tend to get involved.
Even if that isn't the case, all those weapons are on the ground or in port at some point. Meaning an attack with small arms to get in there and preemptively blow them up will work. These weapons also have to be maintained meaning they need a base. You have millions of citizens with weapons and a military that's a much smaller fraction of that, with bases that have a much smaller fraction of personnel. The base is going to be overrun. There is also the chance of military personnel defecting, so that some of these weapons never get fired.
Chemical and biological weapons are a really bad idea. The problem is a civil war isn't going to be geographically defined in this case. There is no polarization along something like a Mason-Dixon line. You will end up killing people that don't revolt, which will probably make them rethink their not revolting. How would you feel if your family and friends were killed in an attack, and they weren't on the rebel side?
The other problem is even if you increase the military's size to win the civil war, you have the second problem of the very people that you could grab immediately to fight are probably going to be a majority of people who have been opposed to gun ownership, don't have weapons and don't know how to use them. It will take time to become proficient and the other side has both the weapons and training.
Even with advanced military tech, the numbers game combined with a guerrilla approach, and the fact these are civilians and it would be hard to identify civilian combatants from non-combatants, will make it a losing battle. We already haven't done well in Afghanistan or Iraq for similar reasons, and despite the enemy being technologically inferior, we have never been able to secure those regions.