I have a subject in uni called "Academic Writing". I don't know if that's a thing in the US or other parts of Europe. But anyways my professor told us that, and I quote "Citing somebodies work means you agree with them.". But I'm not sure how true this is, like I've read a lot of works before where the author cites somebody else, just to sorta highlight their beliefs about a particular issue. What do you all think?
You do not. In fact, in most cases, I would think that readers assume that a citation is a neutral statement of fact such as in the following:
This question has also been investigated by Smith et al. .
There are of course cases where a citation is clearly an endorsement:
In the excellent article by Smith et al. , the authors investigate this question.
And then there are cases where you clearly disagree with a paper you cite:
We agree with the summary presented in Jones et al. , but note that others have come to conclusions that are either in contradiction to the data we present here (see, for example, Smith et al. ) or have used methodologies we believe are not adequate for the question they investigate (e.g. Kavanaugh et al., ) or are clearly nonsensical (Thomas et al. ).
In other words, context matters: You can clearly express what your position is on an article you cite.
Your professor seems to be thinking of a case in which you use (and cite) the work of another to support (or background) your own work. There are other reasons, however. In fact, in a critical response to an article, you cite it precisely because you don't agree with it.
So, it depends on your reason for citation. Sometimes, in academic writing, it is even necessary to give contrary evidence when you think that your evidence is stronger in a different direction, just to give the reader a full picture.
But, normally, when you disagree with an author you cite, you say something about why you disagree.
Consider if you were writing a scientific article as a response or rebuttal to another (methodological concerns, misinterpreting data, the field has changed around the original work and what was once considered true maybe no longer is, etc.) This happens fairly often in my field, and a healthy sense of skepticism and replication is good for science. You should still cite the original work, even if you're spending many hours, pages, and words to outright disagree with and deny the claims of the original!
Citing material certainly does not mean you agree with it. For example, rebuttal papers need to the cite the paper that is being rebutted yet clearly do not agree with the result.
However, we don't live in a perfectly rational word. Often papers and careers are judged heavily by citation counts. With such a metric, there's no differentiation between "cited because we thought it was good influential work" and "cited because we believe the conclusion was flawed".
In this light, I think the most generous (but also pessimistic) interpretation of "Citing somebodies work means you agree with them" is that you may write a rebuttal but it's possible that the increased citations help the author's career, unless you are really able to turn the tide of opinion about their work to the larger academic community.
Short answer: no.
Mainly commenting to add my theory on where your professor might be coming from. I have a background in both social sciences and STEM - specifically Cultural Anthropology and Computer Sciences. In my observations, it's diametrically opposite situation in both - in the first you'd constantly be reading academic papers based around disagreeing with someone else's research/conclusions. But in CS, my impression was, the base would be multiple papers justifying your thesis and the author in a way continuing the thread of inquiry.
Now the even more subjective part of my answer. Honestly, I think disagreeing, even in academic circles, is more salacious than agreeing and continuing the same work. But in STEM it's harder to argue against hard facts, hence you don't see it as much.
Therefore my assumption is your professor is from STEM background where you can literally name the people who disagreed with prior research because it was that groundbreaking. Eg, heliocentrism, gravity, quantum mechanics all redefined our understanding of the Universe and we don't see papers like that on the daily in STEM.
But if you're working with topics that might be a step towards the social sciences side, eg, human–computer interaction, it's all the more important to be comfortable with disagreeing with prior research. And since you're asking such a valid question, I think you're on the right path when it comes to having the gall to simply question things.