The fact that he did it at the DMV, as opposed to on a public sidewalk, changes the level of first amendment protect that this preacher enjoys. A location traditionally or specifically designated for public discourse is much freer than one that is not. The fact that a location is open to the public doesn't actually make a difference. This why a government building is open for demonstrations, and the captive audience doctrine doesn't apply, because such places are traditionally (in this country anyway) subject to protests and demonstrations. That's the exact place you go to do that. A Starbucks, on the other hand, is not. Nor is a fire house, which is just as much government owned as a town hall.