Look, I'm not aligned with any political movement and my political beliefs are nowhere near the right. But I have noticed on Wikipedia that some left-aligned claims are presented ignoring objections or without any supporting references, while right-aligned claims sometimes get stuck in endless arguments despite the availability of supporting references. I admit that this is just an anecdote. And since I don't read every Wiki article very critically[1], not a lot of them have caught my attention either. So my observations could be just statistical outliers. But this isn't the first time anyone has accused the Wiki of left-leaning bias. Meanwhile, I'm yet to see anyone accusing it of right-leaning biases, outside of organized vandalism campaigns. It is widely suspected that these biases come from the Wiki editors themselves[2].

Considering how much the information on Wikipedia influences politics and people's lives these days, it's important to not simply brush such concerns aside. It's a difficult task to address it, but may be well worth it. As a first step, someone will need to do a statistical study of a large sample of arguments and claims that lack supporting references. Only that measure will establish if the concern is real or just imaginary. Whatever comes after depends on that result.

Whatever be the truth about this accusation, there is something else very clear that prompted me to write this reply. Left ideology doesn't automatically equate to liberalism. I've noticed that a section (not everyone, but a sizable group) on the left is very inflexible in dealing with opposing views[3]. The left is the birth place of the cancel culture after all. They don't tolerate any challenges. However, that attitude is very detrimental to an information repository like Wikipedia in the medium to long term. The only real solution is to embrace the true progressive ideology - depend on evidences rather than conformance to popular narratives.

[1] I'm just looking for starter information most of the time. Critical analysis isn't the priority there.

[2] I'm not making an accusation. Everyone has biases. But it's important to address them in contexts like that of Wikipedia.

[3] The incident that made this very clear to me was when the fediverse almost defederated (cancelled) the fosstodon.org instance. It was over something that one of its right-leaning admins said somewhere else. That ultimately didn't happen because the said admin resigned and the instance moved to a more formalized administrative protocol. However, even that's a bit too far, because that admin had kept his job free of his personal political beliefs, and it never reflected on the instance. Besides, that instance is also home to a lot of individuals and FOSS projects, the majority of whom are left-leaning. The use of cancel culture as a weapon for stifling political speech was on full display there.