What is a Critical Scholar?

Jon D. Levenson, Professor at Harvard Divinity School in the Department of Near Eastern Studies and Civilizations, offered a great definition of what a critical scholar is when he wrote they “are prepared to interpret the text against their own preferences and traditions, in the interest of intellectual honesty.” See page 3 of his book The Death and Resurrection of the Beloved Son. In that book he argues that "only at a particular stage rather late in the history of Israel was child sacrifice branded as counter to the will of YHWH and thus ipso facto idolatrous" (p. 5). Why shouldn't all Biblical scholars be critical scholars?