Sorry. They're right. Not about feeding on "dirt", but you will breed bugs. Moreso with soil. That's not hydro. That's a potted plant. Hydro is generally considered soilless. Can't think of any bugs that will be breeding that require spraying, though. I've had indoor plants for years and never sprayed once. More concerned about the health of my family and pets than the convenience of not having to swat an occasional bug. Usually people just have to deal with fungus gnats. Those are pretty easy to take care of. If the water is stagnant, it can breed mosquitoes. Never let water go stagnant.

As far as your comment about showing them they're wrong. . . If you live with your parents, I'm of the opinion you need to do what you are told unless you are paying a fair rent and they rely on it. Otherwise, you are essentially a guest in their house (yes, even if you are their child) until you can get your own and you owe them at least the respect of abiding by their rules. That goes for anyone's house you stay in that you aren't paying substantial rent at. Even if you are paying rent, you have to obey the rules. In the adult world, if an apartment complex or landlord of a rental house say no plants or animals you abide by it or you get kicked out on your butt. It's that simple. In other words, you can't show them their wrong. Their rules = they're right.