1. This
estimate gives a number of 4,700-- a number that is greater than the number killed in the US by Muslim terrorists.
2. There is a strong connection between groups that are explicitly religious and extremism. The best known example is the the KKK groups (historians will point out that the modern group of this name differs from previous incarnation); the KKK groups have always claimed to be doing the work of Christ and has drawn much of their rhetoric from the Bible.
These Christian extremist groups have been responsible for thousands of deaths. They are still spouting hatred, but have held at bay for some time.
3. If you want to look internationally, there are many modern Christian groups that have advocated and committed barbaric acts of violence. I would include the Lord's Army (and similar groups) in Africa and Mislosavic, not too long ago in Europe.
4. There is no real threat that violence will have any significant impact on our government (other than to give Republican even more power by a public reacting to fear).
The implicit threat that I think Foxfyre was raising is that Muslims would enter government and then start mucking with laws.
Of course there are other reasons that this fear is completely ridiculous
1) Americans of any religion have the right to enter political office and change the laws. Since Muslims are a minority, any change would need support from other religions-- and if enough American support a change in law, that's democracy.
2) The Christian Conservatives (the group from which Foxfyre hails) is doing exactly what she accuses the Muslims of doing. Of course they are not having much luck recently owing to the fact that most Americans think they are full of crap.
3) The conservative Muslims and Foxfyre would probably agree on most laws. They would ban homosexuality, enforce public morality (particularly on the airwaves), support capital punishment, promote a vigorous national security policy.
But the point is this. Under our laws... all religions are equal.
Personally I have the same opinion. If a religious person is moderate, and reasonable on how they pursue their political goals, I can respect them. If they are obnoxious and trying to force their beliefs on me (particularly by enacting conservative laws on social policy) I get annoyed (but accept their right to do so).
Of course we should oppose extremists. But, they should be opposed because of their extremism-- not because of their particular religion.
To say there are no Christian extremists... or that Christian extremists shouldn't be opposed is lunacy.