Not to insult your father, but that's completely false
I've been a very healthy vegetarian (with no dietary professional assistance) for six years, and while I don't avoid beans, I make no conscious effort to eat them. They crop up every once in a while in my food, but not often enough that they would influence my health in any way. It's a common misconception, though. Since we were kids, health programs have been telling us that the way to get protein is through either meat or beans. That's not true, though; there's protein in pretty much everything healthy, especially dark leafy greens. As long as you keep a variety of foods in your diet, don't worry about the bean thing. Also, if you find your father pressuring you about protein, try "fake meat". Boca and Morning Star Farms and many other companies make "meat" like fake burgers and such out of soy... which is technically bean!