Douching is also bad because, some girls and women used to think (maybe still do?) that douching after sex could help prevent pregnancy, by washing the sperm out, but it actually increases the risk, because it washes upwards first, pushing the sperm into the uterus area. This is also why you're more at risk for developing yeast and other infections, because it pushes the bacteria further into you.
You're also not supposed to do colonic irrigation, except perhaps if a doctor tells you to. Some people do it as a health fad--there are actually centers where you can just go in and get a colonic! But you can weaken your rectal muscles and even make it so you can't poop properly. Again, your body has its own way of cleaning you out. If you want to help your body, drink lots of water, and don't eat heavy or unhealthy foods.
And okiedokie, that was great, about the TV repairman!