You might just as well argue that "Children of Earth" clearly shows that the military and intelligence services should be abolished. They're just too dangerous to be kept around. At some point someone is going to misuse them.
Or maybe "Children of Earth" shows that the United Nations are evil and should be abolished, since UNIT personnel effectively takes over the UK government during the crisis and orders to take the children by force.
Or maybe "Children of Earth" shows that the United Kingdom should withdraw from NATO, since it's mostly U.S. military personnel which effectively takes over the UK government.
So, "Children of Earth"'s message is basically anti-military, pro-gun, anti-UN, and anti-American.
Or maybe it's the best if you don't see any political message in "Torchwood"... there really aren't many.