Actually, you can. Though I'd most likely choose the route of minding my own damn business, unless it was a rape or something obvious. If two people are beating the shit out of each other, I'd probably look the other way.
Page 23 of Ohio's current Concealed Carry Law handbook:
-Defense of Others:
A person may defend another only if the protected person who would have had the right to use deadly force in self-defense themselves. Under Ohio law, a person may defend family members, friends or strangers. However, just as if he were protecting himself, a person cannot use any more force than is reasonable and necessary to prevent the harm threatened.
Basically, you can only protect a person if they are deserving of protection.