Why is this wrong? Please explain to me?

Maybe some of you have seen my question about putting Holy Water in my sanctuary that I'm building. And many of you said that it is idolatry and that I'm putting it before God? I don't see how that is. How am I putting it before God? I'm building on because it is beautiful. And it's a great way to worship and pray. The have one in my church!!!! Kneeling stools, statues of saints, beautiful lit candles, and crucifixes! So why is it wrong for me to do just that, but put it in my own home? I'm not putting it before God at all! If that is before God, then you're basically saying that all things used for worship are. Such as the bible and the rosary. Please explain to me, I don't understand.