You've opened quite the can of worms here, my friend.
Red-tailed boas do get rather large, especially to someone who has only had ball pythons in the past. Yes, they have the potential to be dangerous, because they're very strong snakes, especially when they're full-grown.
However, they are very docile in nature when brought up with the right husbandry and the right feeding schedule. As an owner you should do the right things to prevent an incident (feed your snake properly, a hungry boa is a more dangerous boa; don't feed the snake with your hands as it will start to associate your hands with food; don't handle the snake right after feeding it or another snake, or while you smell like rodents, etc.)
Think of it this way: Is a car dangerous? Well, it can be, if you don't know how to drive.