why do they think can decide what content you want to be downloaded through your internet connection and displayed on your devices? once the bits & bytes enter my network, you're free to do with them what you want, they have no say in what is done with that data. If it's filtered, that is not their decision to make
I don’t know that “I don’t understand why they are mad that I’m stealing from them even though I agreed to pay for the cost by watching ads” is really the argument that you are hoping for. YouTube is a business and delivering video costs a significant amount of money. If you want to use it you are agreeing to watch ads to pay for that costs or to pay for a premium plan. At least be honest with yourself about the situation, and this comes from someone he vehemently hates ads as much as the next person, but that is “the cost of admission” so to speak.