Sure there are Christian terrorists. Who do you think Timothy McVeigh was when he blew up the Federal Building in Oklahoma City?
There are right wing white supremacist and hate groups all over the United States and every last one of them is a terrorist. Here are some following recognized definitions for terrorism:
S:

terrorist (a radical who employs terror as a political weapon; usually organizes with other terrorists in small cells; often uses religion as a cover for terrorist activities)
S:

terrorism, act of terrorism, terrorist act (the calculated use of violence (or the threat of violence) against civilians in order to attain goals that are political or religious or ideological in nature; this is done through intimidation or coercion or instilling fear)
What do you think right wing hate groups do? They get out their guns and threaten with their presence. One of them recently showed up at an Obama speach with an AK47 assault rifle. His very presence was a threat to the President of the United States, and the weapon constituted a "threat," The problem is, the US Government has not yet decided to enforce Presidential Protection Laws...which need to be enforced. I am wondering why the Justice Department and Homeland Security did not arrest the individual in question. We need to definitely make a point by arresting an imprisoning internal terrorists like this. There is no difference in my opinion, between threatening to do something violent and actually carrying it out.
Here is a definition of terrorism defined by United States Law:
http://terrorism.about.com/od/whatisterroris1/ss/DefineTerrorism_5.htm
United States Law Code – the law that governs the entire country – contains a definition of terrorism embedded in its requirement that Annual Country reports on Terrorism be submitted by the Secretary of State to Congress every year. (From U.S. Code Title 22, Ch.38, Para. 2656f(d)
(d) Definitions
As used in this section—
(1) the term “international terrorism” means terrorism involving citizens or the territory of more than 1 country;
(2) the term “terrorism” means premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents;
(3) the term “terrorist group” means any group, or which has significant subgroups which practice, international terrorism;
(4) the terms “territory” and “territory of the country” mean the land, waters, and airspace of the country; and
(5) the terms “terrorist sanctuary” and “sanctuary” mean an area in the territory of the country—
(A) that is used by a terrorist or terrorist organization—
(i) to carry out terrorist activities, including training, fundraising, financing, and recruitment; or
(ii) as a transit point; and
(B) the government of which expressly consents to, or with knowledge, allows, tolerates, or disregards such use of its territory and is not subject to a determination under—
(i) section 2405(j)(1)(A) of the Appendix to title 50;
(ii) section 2371 (a) of this title; or
(iii) section 2780 (d) of this title.