Not only is science inseparable from ideology, but they idea that it can be separate is itself ideological. Let me explain, point by point.
1. When people say that science is above and beyond the realms of ideology they invariably point to a concentration on a detached observation of natural facts and make recourse to some universal scientific method as the distinguishing features. But there is some circularity and even hoodwinking here. Firstly, if the facts of science are the product of a detached observation, it doesn't follow that that which is being observed has a real existence in nature. In order to decide what to observe, never mind how to observe it, a series of value judgments must be made. Take evolutionary theory. While I am convinced of its truth and its intellectual power, I cannot see how one could possibly say that it was produced by detailed, clear, unbiased observation of natural facts. Nobody has ever witnessed in any real sense evolution by natural selection. Certainly, as a deductive assessment of how we have come to have myriads of different species is convincing. But we can ask why it came to the fore, independently by two scientists - Darwin and Russell Wallace, both of whom grew up in industrial Britain in the early nineteenth century, when it did and why it was formulated in the way it was. The context of these scientists lives shaped the way they viewed the natural world. To my mind, they couldn't do otherwise. Competition between distinct groups for scarce resources has a definite resonance with the period and place in which these theories came to the fore. Yes, you might say, but now we know better. But can we really say that? Aren't we as much products of our times as they were of theirs? To underscore this point one only needs to look at the metaphors which are currently used as observational categories for understanding the human mind. In the 1820s and 30s, when Darwin and Russell Wallace were formulating their theories, the mind was understood as a steam engine. Today, the metaphor is the computer. We all know why.Let's stay with metaphors a while. Natural selection is itself a very powerful metaphor. To select assumes that a judgment, somewhere along the line, has take place as to what is good or better and what is bad or worse. That is ideology in action. But selection also suggests a selector. Who or what does the selecting? Whatever you want it to be - God, genes, nature - it has selected; engaged in a moral action and all ideology depends on a moral viewpoint. But let's move away from nineteenth century biology for a moment and take a look a contemporary particle physics. The number of elemental particles has mushroomed in recent decades, yet, like the 'fact' of evolution, nobody has ever seen them directly. They have to be inferred from our observational techniques (smashing particles together). Strings and superstrings, extra-dimensions and such esoterica only really exist as mathematical models. Compelling, intellectually convincing, probably accurate description of how things are. Mathematics, I hear you say, is surely above ideology. Well, no. Arithmetic truths cannot proved, for example. I'm not saying that therefore they don't exist. Rather, I'm saying that to see them as truths we have to take a leap beyond the observational and that put mathematics in a more ideological - some would say theological - realm. And this leads us to the second half of this point - The Scientific method. A method of acquiring truth must use our very human (and therefore political, moral, ideological, call it what you will) capacities to observe. Our senses have been repeatedly shown to be untrustworthy, our language imposes categories on whatever nature might 'in reality' be and our minds are at least in some way conditioned by the time and place in which we find ourselves. And then why do people insist on referring to The scientific method? Whose scientific method? Which one? The inductive processes of classical physics are radically different from the deductive framework of biology. Quantum physics even put the methods of observation right in the middle or what is being observed. A paleontologist would be very hard pressed to explain the fossil record using the analytical methodology of a chemist. There is no single methodology in science. There are several. And I would say this is the case because in order to observe something we must formulate, socially and individually, intellectually and ideologically, at least some idea of what it is that we are observing.
2. My second point refers to how science works as a communal enterprise. Several studies, usually taking their cue from Thomas Khun, have pointed out how change in science occurs and how emphasised the role of science educators, journals, peer review, scientific training and other such ordinary everyday, one could say anthrpological, features of making science above the actual ideas themselves. This is not to say that the ideas and new observations are of no importance. They clearly are. Rather, the point is that alone they are not enough to affect a change in what is considered scientific truth. Such a change must rely to some extent on the institutional and interpersonal aspects of science as a public endeavour and these aspects, inevitably, are tainted with ideology.
3. That science itself has lent itself so readily to what nobody would dispute as ideological causes surely says something about the ideological nature of science itself. Racial theories (both supremacist and egalitarian) which deployed evolutionary theory as a supporting theory; Marxist science in Stalinist Russia (think of Lysenko); perfectly rational Aristotelian physics in support of an earth-centered cosmos; Quantum physics to support Oriental mysticism - the list could easily be extended, but each one highlight the ease with which science and ideology permeate each other. Again, I'd suggest that this is because they are so indistinct to begin with.
4. If all this is true, we must ask why it is that some people claim that science is above ideology. Well, take a look at who is claiming this. Scientists. For historical reasons, men of science have had to wrench control from other groups (gentlemen, clerics, etc.) in order to have the political clout to say how things are. The professionalisation of science from the seventeenth century to the twentieth is the history of a struggle for control about how has the social-political-moral right to issue truth claims about the world. I don't want to say that the claims aren't true. Just that the claim that science is free from ideology is itself an ideological claim aimed to bolster the position of scientists as producers of truths. Just as reniassance and medieval clerics made recourse to the word of God to bolster their position as truth-makers.