Originally Posted by Karl
The UN is not communist nor could it possibly be communist. You torture the English language when you say this. To your question, why does it matter how old they are? It matters because of personal agency, it matters because fighting in a war is an adult decision that should be made by adults, it matters because when kids fight in wars it usually is an adult's decision at the end of the day and the child has been taken advantage of. And it matters because the mental strain of war is too much for a lot of adults, and for all kids. It messes them up, even Muhammad laid age restrictions on enthusiastic young fighters. It's in your hadith. Am I ageist? No, I don't believe this qualifies as prejudice or discrimination. It does have something to do with age, but it doesn't have anything to do with prejudice or discrimination.
Now, in a state of war, it does make a certain amount of sense for every able bodied male (of legal age) to serve his country. Along with any able-bodied female that is capable of doing the same job, if I may say so. Or are you sexist? Getting back to the point, though. Able bodied people who wish to serve in such a capacity should only do so by joining the actual military of the country in which they live. Forming a violent non-state entity is not okay with me, for so many reasons, not least of which is the tendency for these types of groups to be completely unregulated when it comes to recruitment (and literally everything else). They can and have, as one example, recruited children as young as 7 for their fight. This fighting should only be done by an actual military though, it should be regulated in what it does so as to prevent abuse, and if the country is a UN member (which every military-having country is), it should abide by the various rules and regulations of the UN.
The UN is not communist in any sense (or any specific socio-political/economic ideology), and it's not insane. Actually, it is the organization that shoulders primary responsibility for picking up the pieces after violent people listen to your bad advice.
Also, Zafran makes a good point.