Last night Ron Paul (who should know better as the only Veteran in the field) had a young Army reservist up on stage to sing his praises. I guess it was a two-fold message from Team Paul; "The military loves me" and "Young people like me".
Sadly, Mr. Paul might have allowed the young man to get himself in trouble. Generally junior enlisted members of the service are not noted for their forethought and critical thinking (I know that there are plenty of exceptions to that statement, but as a former Naval Officer, I think I can make that statement with some authority). So letting the young man get up and make a speech endorsing Paul while in uniform was just not a smart thing to do, especially for he young man who spoke. The young corporal is a "selected reservist", in other words not presently on Active Duty, but that's almost a distinction without a difference since he's still serving and his actions give the appearance of impropriety.
While I am not a military lawyer, or any kind of lawyer at all, I do know enough about the UCMJ and regulations to know that the corporal's actions are a gigantic no-no (see the linked article from Army Times). It's not a question of free speech, because when in uniform and in the service you give up a lot of those rights that the normal American can enjoy and claim, that's just the way it is and everyone learns it in whatever training pipeline brought them from civilian life into the military.
I hope that the corporal doesn't face any more than an ass-chewing from his CO, I don't think he meant any harm and was just a bit starry-eyed (he called Paul "a rock star") when asked to come talk at the rally not thinking of the legal ramifications of his actions.