This is aimed at some of the other comments but: Any non-technical degree comes with some ideological perspective.
Consider Shakespeare.
If you just consider him "great", and read him to appreciate him, then that is an ideological perspective.
You could say the way he treats xyz is a product of his times, that is a perspective.
If you say, he is over-rated and people have held him up to a high standard, that is also a particular ideological perspective.
Having a particular ideological perspective, and arguing against others does foster critical thinking, as long as you are arguing against another ideological perspective.
So if someone says, hey side X was the righteous side in this particular war, and someone else says no it was side Y, and a third person says they were all dirty, that's probably a good thing. It doesn't mean you can find a non-technical discipline free of ideology.
Technical fields -- especially those closer to technology than to natural science -- can also be extraordinarily ideological. Both in curriculum and (especially!) in culture.
For a perfect example of true ideology in action, look no further than these comments -- from members of a field renowned for epic religiousity over such comparatively inconsequential topics as programming languages, text editors, and software license preferences -- decrying the proneness of other fiends to ideological attachments!
On the contrary, the answer to such a question perfectly illustrates the sort of critical thinking that is taught in a history degree program but not necessarily in a technicaly degree program.
After reading enough about the history of mathematics, it is nearly impossible to arrive at the conclusion that today's mathematicians do not have their own set of ideological beliefs. However, obtaining high scores in a mathematics degree program is easily achievable without seeing these beliefs as ideological ("that's just how it's done" is a profoundly common and profoundly ideological answer to questions of the form "but why not do things this other way" -- especially in upper-level undergraduate mathematics).
All degrees bar philosophy come with bundles of ideological perspective.
To truly think critically you must free yourself from ideology as best you can.
The demarcation between the humanities and social sciences and the so-called hard(er) sciences is not a division of technicality. To say that you can split the degrees awarded by our academic institutions into technical versus non-technical and then claim that the more technical are freer of ideology is a supremely ideological statement.
Also, you've managed to conflate not two but three distinct ideas in order to make the claim that you've made: for the purposes of this conversation subjective judgements come in two flavo(u)rs - the first is where you evaluate according to some standard, the second is where you impose your values. It is only the second of these that can be in any way said to be ideological and only then it is only when you become identified with the values you are imposing on the world which happens rarely - and get this, people in technical degrees do this all the time.
In practice, though, postmodernism (taken as a whole) most definitely has an ideology. So did logical positivism.
And even more in practice, if you go to a university to study philosophy, the philosophy department at your university will definitely have an ideological bias.
For this discussion, we might have to distinguish between continental philosophy and analytic philosophy, and then talk about how each is biased in their own way.
Continental philosophy is, in one sense, about the bias inherent in all thought.
One might say that analytic philosophy is about finding the bias free portion of thought, and judgments differ on whether they succeed.
Richard Rorty would be an interesting example of a critique of the second sort of philosophy in this context.
So the fact that I like peanut butter and jelly is not derived from a particular ideology.
It seems to me that it would need other things -- many people banding together, promoting it, fighting against others in various forums -- for it to be called an ideology.
I guarantee that someone somewhere has written an economic explanation of your fondness for PB&J. And someone else has used that to prove that you're a fascist.
Consider Shakespeare.
If you just consider him "great", and read him to appreciate him, then that is an ideological perspective.
You could say the way he treats xyz is a product of his times, that is a perspective.
If you say, he is over-rated and people have held him up to a high standard, that is also a particular ideological perspective.
Having a particular ideological perspective, and arguing against others does foster critical thinking, as long as you are arguing against another ideological perspective.
So if someone says, hey side X was the righteous side in this particular war, and someone else says no it was side Y, and a third person says they were all dirty, that's probably a good thing. It doesn't mean you can find a non-technical discipline free of ideology.