I think it all depends on the facilities and the people there. I have, in the past, boarded at a facility with a stallion. The stallion was in the main barn, but in an special "stallion" stall, was in a special paddock (probably two to three feet higher than all of the other paddocks) that was very sturdy. At my current barn, I would be a little leery if a stallion was brought in because I don't trust the fences.
But as long as there are extra precautions to make sure that the stallion(s) don't/doesn't get out and are handled properly, I don't see a problem with it.
"You know, for as long as I can remember, I've had memories." ~Colin Mochrie