In the eyes of the law, anything can be viewed as a weapon in the right context. Since you decided to start a thread inquiring about this subject, I can only assume that you intend to fit that context like a glove. I'm not saying that you will get arrested for merely having a baseball bat in your Jeep, but it will certainly throw up red flags to any cop with half a brain. Unless you can prove that you are going to, or coming from, some sort of baseball/softball event you will, at best, get hassled and earn yourself a spot on that officer's radar, and at worst, get charged with carrying a concealed weapon. Furthermore, the minute you decide use it for anything beyond baseball it automatically becomes classified as a potential lethal weapon and your day becomes extremely shitty, extremely quickly. It will make your subsequent self defense argument a much tougher sell, that is, if your lucky enough to even be able to mount a defense and not lying in the morgue with a 45 cal. hole in your chest.
What I can't figure out is, why, as an American citizen, you wouldn't just apply for a LTC permit if you are legitimately concerned about your safety? Are you a underage? An ex-felon? A baseball bat is only going to get you jammed up or killed.
The most important thing you can do in the event of an attack is to create distance between you and your attacker while still having force options at your disposal if necessary. If you are truly only concerned about self defense, deescalating situations should be your only concern. Carrying a baseball bat around hardly seems like something someone who is concerned solely with self defense would do. I'm not saying it's impossible, but with a plethora of better and smaller weapons available, carrying a baseball bat just makes it seem like you're trying to disguise your intentions. Having a license to carry permit will keep you as safe as you can hope to be in the most efficient, lawful manor possible. Pass the proper courses and go through the proper channels and you'll never have to worry about being hassled.
If your only concern is road rage, punch "The high road" into your GPS and see where it takes you, you may be pleasantly surprised. If you have legitimate concerns about you or your family's overall safety, then by all means go out and get yourself a license to carry a firearm. Treat it with respect and be aware that any weapon can very easily be used to take someone's life...or your own.
