An element of many crimes is intent. Prosecutors often are able to prove intent to the satisfaction of a jury.
In this case, we probably don't have all the information, but it's quite possible that the training included literature or documentation from which an intent to "further a civil disorder" could be inferred.
"It is long been a principle of ours that one is no more armed because he has possession of a firearm than he is a musician because he owns a piano. There is no point in having a gun if you are not capable of using it skillfully." -- Jeff Cooper