What reasons do conservatives give for wanting to downplay Thomas Jefferson's role in history in Texas textbooks?

Conservatives supporting this curriculum change in Texas
history textbooks clearly have a conservative agenda which includes a dominant Christian
influence. Their attempt is to present the founding fathers as fundamentally Christian
as well as stressing the impact of conservative politics; notably in the last century by
including figures like Newt Gingrich. 

But Clearly, the
main reason they are opposed to Jefferson is that Jefferson is credited with
establishing the precedent of separation of church and state.  Although the First
Amendment does not come right out and say this, it is implied as Jefferson believed
religion is between the individual and God; not to be mediated or endorsed or limited by
any government. Jefferson's letter to the Danbury Baptists in 1802 is the source most
often quoted in this debate where, in support of the Danbury Baptists' right to
establish their religion, he used the term 'wall of separation between church and
state.' The First Amendment reads:

Congress shall make no
law respecting an establishment of religion, or prohibiting the free exercise thereof;
or abridging the freedom of speech, or of the press; or the right of the people
peaceably to assemble, and to petition the Government for a redress of
grievances. 

Since the First Amendment implies that the
government will not establish nor limit any religion, the wall Jefferson referred to in
his letter is 'built' to maintain that religious freedom and to keep religious biases
from intruding with political progress. 

The Texas Board,
openly conservative, endorsed by Don McLeroy, a self-described 'Christian
Fundamentalist,' is making the point that not only is America moving to the right, but
that it has been a conservative Christian nation since the Founding Fathers. The Texas
Board is essentially ignoring the Constitution by attempting to introduce political bias
and their brand of Christianity into public schools, which are a government
institution.

Not to mention, their other agendas in science
books (using I.D. to challenge Darwinism, where again, the matter is subject to debate,
but the consensus is that this is another debate between religion and science; not
science and science).  Ergo, I.D. should be taught in a course on Theology or, at best,
theoretical science/philosophy.