People who believe taxation if theft, I would have to imagine at least don't believe in notion of government and society, at least the idea of a country. If you believe in having a government and a country then those things have to be funded. And who best to fund them than the people who receive those services. If taxation is theft, than so are dues that you pay at a club, or a union that you're a member of. Because those organizations take your money as well and you don't get to decide generally how much you're going to pay them. They do that for you.
Someone could say that people choose whether or not to join clubs, so they're choosing to pay those dues, because they've made a choice to join that club. But we also choose what country we live in. Or at least what country we want to live in and then the country decides for itself who should and shouldn't live there. If you think taxation is not theft, try finding a free developed country that doesn't have taxation. You might have the same luck finding a club that doesn't have dues. Someone has to pay the bills and again who more qualified than the people who receive the services of the club and government.
In the video several people correctly answered the question what is theft. Taking what doesn't belong to you without your permission. If taxation is then so is club dues. When you choose to live in a country or be a member of a club you're also choosing to follow the rules of the club and the country. Paying your bills are one of those rules. You don't like the rules of the club or country, well in free societies you can work to change the rules. Demand lower taxes and dues. Vote out people who you believe tax you too much. Vote in people you believe will cut or eliminate your taxes. But as long as you're a member of the club or country you play by the rules, or deal with the consequences.