"The pair of you would like to have the right to have a tank...".
Well, now we are getting to the heart of the issue. Piers, it is the people who have the right to keep and bear arms, government has permission to use weapons in their duty to protect the rights of the people and defend the constitution. The issue is not whether people need a particular type of firearm, the issue is that the government may not make that decision. It is clearly defined in the second amendment that the right to keep and bear arms may not be infringed.
See the following. http://goo.gl/QEGJi