If a scientist studying cancer calls cancer terrible in a casual conversation, they can still produce valid rigorous work about it. We'd have approximately zero research done if we disqualified everybody with a personal opinion about what they're studying. No one's unbiased, but basic science methodology helps us reveal and eliminate/compensate for our biases.

It doesn't matter whether you personally think oppressing human freedom is terrible or not—your work will not be any less useful. Its results may even challenge your own subjective opinion on the matter.

> To do a "proper study" you should be impartial

Why do you believe this? It is very much not true. If you wanted to study, for instance, how societies collapse, you don't need to be impartial about the notion of societal collapse. If you wanted to study war, you don't need to be impartial to war.

All science starts with a hypothesis and many of those are rooted in partiality. The point is to have an investigative method which proves or disproves that hypothesis.

The fact that science reveals truth even though it can start with partiality is why the scientific method is the gold standard.