@croydon - People should just eat the right food to prevent constipation in the first place. Even if you aren't fond of vegetables, there are other things you can eat that will provide more than enough. Oatmeal for example, even oatmeal cookies, can help, as can dried fruit like dates (which are essentially like eating candy).
Even if you are someone who likes to eat a lot of processed foods or meat, you can work out some way of including fiber. It won't do you as much good as a properly diverse diet, but it's better than not having any fiber.
Constipation might not be much fun, but lack of fiber can cause much worse problems, such as cancer. So this isn't just about preventing hemorrhoids, even though that should be enough of a goal.