First, a matter of definition. I differentiate ideology from ideation. Ideation is omnipresent wherever people think. It is the work of what Lonergan calls intelligence: the formation of concepts to articulate the insights generated through attending to the data. Still following Lonergan, I define ideology differently. If the work of knowing is to attend to the data, to produce intelligible concepts to articulate the insights generated by attending to the data, to render reasonable judgments about the adequacy of those concepts, and to act responsibly in light of those judgments than ideology is the attempt to justify a recurrent failure to be attentive, to be intelligent, to be reasonable, to be responsible. Rather than undertake the difficult work of correcting one's inattention, unintelligence, irrationality, or irresponsibility one invests one's energy in either presenting oneself falsely as all those things or critiquing the very idea that one should be any or all of these. Often this is done by appeals to just one of these four steps: knowledge is said to be only seeing, as in empiricism; knowledge is said to be only ideas, as in idealism; knowledge is said to be only judgment, as in authoritarianism; knowledge is said to be only responsibility, as in moralism. These are the sort of cognitive ailments that I gather under the rubric of ideology.
In order to think about what this means for scholarship let us consider my own obsession, the dates of the New Testament texts. I think that J.A.T. Robinson was more right than wrong: the bulk of the New Testament was written between 30 and 70 C.E. Now, saying such is enough in many quarters to render myself immediately suspect of ideological interference. Many will assume that I just must be a fundamentalist who is engaged in the apologetic defense of traditional Christian doctrine. The problem is that this judgment doesn't follow, and this for several reasons. First, a problem of attention to the data: empirically, the aforementioned J.A.T. Robinson was almost expelled from the Church of England for articulating quite non-traditional theologies, and as such it becomes demonstrably the case that the one scholar that has argued at length that the New Testament texts were written between 30 and 70 was not engaged in the apologetic defense of traditional Christian theology. Second, there is a failure in thinking intelligibly about the suppositions and consequences of the hypothesis. When you reckon that the majority of scholars would date the bulk of the New Testament texts to the years between 50 and 90 C.E. it turns out that all I advocate is a downward revision of the range in which they were written by about 20 years. I cannot think of a single Christian doctrine that is dependent upon or is even made more reasonable by making that 20-year revision, so it is far from clear what Christian doctrine is being defended by this hypothesis. Third, there is a question of reason, for if the suspicion of ideological interference is used to reject a position then there is a genetic fallacy operative in the decision-making. Just because a position is adopted due to ideological interference does not mean that the position is false.
Given these problems, if suspicion of ideological interference is used to reject an argument on such a matter as the date of the New Testament texts then such rejection itself would stand as evidence as ideological interference. The one rejecting the hypothesis might actually be correct in so doing, as the hypothesis might well still be false, but that person has not actually shown that it is. She or he doesn't know that it is false, but rather finds it cognitively expedient for it to be. As such, ironically, perhaps nothing is more indicative of ideological interference than an evaluation of a hypothesis that considers not the empirical, intelligent, and rational warrants adduced by its proponents but rather proceeds by analyzing their implicit or explicit ideology. Such ideological analysis has a place, but it does not substitute for careful consideration of actual evidence and argumentation. Such careful consideration, the operations of attentiveness, intelligence, reason, and responsibility are ultimately the only effective antidote to ideological interference, in our field or any other.