Matthew,
I am a Christian Zionist.
I've always found this a curious position for Christians to take. I know that there can be many shades of this, with differing rationales, but my understanding is that the Zionist position breaks down into two basic versions...
Religious Zionism : This would be the position of those who believe the Jews have a right to their own state on religious grounds (basically, "God gave them the land", and unconditionally so).
Secular Zionism: This is the position of atheistical Jews, and those non-Jews who believe Jews "deserve" their own homeland, on the basis of "anti-Semitism" being such a problem that Jews will never be happy or safe unless they have their own state. Interestingly, this is the thinking of the original Zionists (who were all atheistical/secular in their orientation; it took a long time for Orthodox Jewry to get on board the Zionist cause, as it used to be commonly believed that it would only be with the "coming of Moschiach" that the Jews would regain the Holy Land) - "religious Zionism" is a later phenomenon.
I believe the arguments in favour of either position are wanting; particularly the "religious argument", and even more so from a Christian perspective. The Jews, while religiously/culturally semitic (and this is the only meaningful way of looking at it - as another poster wisely pointed out, the "racialist" views are distinctly modern, not to mention erroneous and dangerous), practice a religion in varying degrees of intensity (from ultra-Orthodox down to "Reform" and "Reconstructionist" Judaism) which is essentially the child of the Sanhedrin that betrayed the Lord and sent Him to His death - and it's been justifying that betrayal in various ways (ranging from denial to
blasphemy) every since. Aside from age old Christian teaching that the Church is the continuation of the Old Testament Church (which, sadly, Evangelical Protestants basically deny), I find it hard to fathom how a
Christian can accept the idea that an unfaithful people are the beneficiaries of promises which in the Old Testament are strictly conditional to their
fidelity. For example, it was because of the unfaithfulness of the northern tribes, that they were invaded and dispersed by pagans - and later it was the ongoing faithlessness of the people which resulted in the expulsion of the Judahites (Jews proper) which resulted in their expulsion the first time around and the destruction of the first (Solomon's) Temple.
As for the secular argument, if we were to take it to heart (including accepting all of the premises at face value; which I do not, btw.) and apply it universally and equitably (though truthfully we are not supposed to do this), it would result in anarchy - since there are any number of disadvantaged people who could (and often do, but usually to no effect) throw up a fuss and demand they be settled in a land ruled by them and for them alone. There are of course, many other well known injustices further associated with the formation of the modern state of Israel to be considered as well.