There are such a wide range of martial art schools now, I think anyone can find a school perfect for them. Everything from cardio kick boxing, to sport karate, MMA (in some states), kung fu, and traditional arts such as Aikido or sword drawing.
Each of these arts has a different energy and state of mind. Depending on what one wishes to get out of a particular style should dictate what art to take up.
Of course, people who go to a dojo looking to beat people up should not get involved in martial arts. Most any experienced Sensei will recognize this and will turn them away.
Great question, I think I know the topic of my next hub!