Term militia is not unique to America. Militias were created and functioned all over Europe. They were never tied to an official military because in many cases the official military was on the side of the evil. One good example could be uprising in Slovakia in which militia was formed against the Slovakian Nazi regime and Germans who occupied the country. This uprising was driven by people who armed themselves and went into the mountains. During WWII. Yugoslavian militia was opposing Italians and Nazis as well as domestic fascists.
In order to form militia you need to have individuals with guns, otherwise you would be forming "dead men walking squads". That would be my argument. Imagine, that your own country is taken over and police and military is suddenly under the new "evil" leadership and you have no guns at all. What would you do?
Another excellent example would be destruction created by UN and international forces in former Yugoslavia in 90's. Over there UN forces created enclaves which were suppose to protect the innocent, those enclaves served as traps in which many unarmed and naive citizens were murdered, raped and brutally tortured. Again, people with weapons formed militia to protect their own communities.
If people give up their rights to weapons they will become easy victims of aggressors. Great example is Czechoslovakia in 1968 when it was invaded by 500,000 soldiers of the Warsaw Pact (mostly Soviets, but also East Germans, Polish and Hungarian forces). Czechoslovakian military stayed in their barracks and so was police. People had no weapons, because communists did not allowed them. So, the invasion was a success and Soviet regime took over the entire Czechoslovakia for 20 years.
I believe we need to get antis from their comfortable position that guns are bad for everybody. Well, citizens who are trained are a big value to any community in the case that such community is in danger.