Because they are both fundamentalists of the double-separatist variety.
Here’s something for John Fea to consider (as he passes on advice to the new White House press secretary, Sarah Huckabee Sanders):
There is a moral argument, I suppose, for men and women who chose to go into this administration to serve in Cabinet-level or sub-Cabinet positions out of a sense of obligation to the country. (The better argument is that working in this administration inevitably leads to enabling wrongdoing and horrible policy decisions, but I understand the rationale of those who disagree with me.) However, there is no moral argument for going directly into the president’s senior/political staff, which in this administration means defending indefensible conduct, denying reality and encouraging others to lie in defense of the administration. You cannot serve in a dishonorable White House honorably.
Now substitute mainline Protestant churches (read modernist) for Cabinet and president in that quotation and you have the same argument that prompted Bob Jones to reject Billy Graham’s — get this — crusades when in 1957 the revivalist started cooperating with mainline churches. It was the same rationale that led the OPC to reject the leadership of the National Association of Evangelicals for including in its membership ministers, laity, and congregations that belonged to the mainline churches. That was double-separatism then, and historians like John Fea who know a thing or two about fundamentalism have argued that such institutional purity lacked Christian charity and was even ornery.
But if applied to the secular realm, such double-separatism makes perfect sense.
Pardon me for thinking evangelical historians are not up to their A-game with Trump. Is it because they’ve gone soft on Russia?