It's not about helping yourself. It's about consistent voting. If everyone votes for the rich person, the entire system will be skewed hopeless in their favor.
You think taxes are unethical? Then how does the government pay for itself? Would you rather they just printed the money they need? That would also be a tax; a flat tax.
And if you don't believe the government should exist then that's anarchist, not libertarian. Though if you want anarchism then you can't have a barter system.
>I'm from Sweden. I understand very well why the Libertarian Party exists. We do have (very small) parties in Sweden which correspond quite well to the libertarian party.
By "very small" you mean "fringe". Like the BNP in the UK no doubt. If you truly have "US Libertarian" parties in Sweden, then how about instead of ruining your country you just move the US so you can enjoy what a Libertarian paradise is actually like.