I don't view taxation as theft and I don't think it's fair to call it so.
The reasoning for taxation is pretty clear - we as a society need public services and we need our individual rights and safety protected and the endeavor to do so requires funding. And since all of us benefit from all kinds of public goods and we have property and earn money in the context of a society kept together by government, it is by no means unreasonable that we would shoulder some of that financial burden.
Still, when governments are corrupt, it's really easy to start viewing paying taxes as a way to support that corruption. I live in a very badly govern country where corruption is really rampant and when I pay taxes, I am absolutely certain that a great deal of those money go into personal pockets, into unneeded luxuries for government officials and very little go into fixing the sorry state of the country. This is why I am reluctant to pay anything I can avoid paying and I view "paying my fair share" to the country as a waste of the resources I have available.
The other caveat of taxes, is that despite the fact that we can say they are reasonable and they are part of the social contract, one could easily argue that they have never agreed to to this, that they don't want any government services and that their money is taken from them by force. Technically, this is indeed the case and taxes are by no means optional.
Still, I support fair taxation and I think taxes are generally something that should rightfully exist.