In terms of specific reasons to doubt the Gaza Health Ministry numbers specifically, I could go on forever about that, but I don't see the point of doing so on HN. It's not a tech-related question.
It feels more like an Israeli attempt at using fog of war and the masses ignorance on the matter to soften the reaction and spread doubt about the real numbers. As this talking point was continously used by Israeli spokespersons even after US officials believed these numbers to be fairly accurate. I would be happy to be corrected, I wish the numbers are actually less, and would want this to be the reality.
https://www.wsj.com/world/middle-east/u-s-officials-have-gro...
How are the numbers generated?
So people are asking you to be scientific and critical rather than to uncritically repeat the claims of a belligerent in combat.
Finally, I'm not sure if you're saying this facetiously or if you genuinely don't know what Israel is capable of, or the lengths its gone to to reduce civilian harm but Israel is not doing indiscriminate mass slaughter. That's what Hamas did on October 7.
I mean completely seriously that Israeli occupation forces are engaging in deliberate mass slaughter, including widely reported upon declarations of certain zones as safe for civilians followed by the bombing of those zones (https://apnews.com/article/israel-hamas-war-news-01-03-2024-...).
While you rely on authorities, I'll do what enlightenment thinkers do. Ask questions like "how" and "what is their method."
None of this is to defend any of the Netanyahu administrations actions in Gaza. I think these discussions on HN are largely cursed, and nobody is going to persuade anybody to "switch sides". You don't have to agree that the UN is, as Israel's supporters would say, so clearly biased against Israel as to be fatal to their credibility. But I don't think you can dismiss the charge easily. If you dig in, you're going to read some uncomfortable stuff.
That's a little glib though, since it's fundamentally not how the UN works.
Since the org is huge, multipurpose and multifaceted (and often less than the sum of its parts), I'd say it's best to stay as specific as possible both when using some UN thing to buttress an argument or to critique the thing - so, what is the thing, by what org, person, representative, etc.
In this case, the specific thing is
an interview with a UN relief director who explained the retrospective examination of past casualty reporting that had happened
Which doesn't seem to be linked? From there the whole thing swerves into a discussion of 'The UN' which turns to vague generalities that are mostly (I think often unintentionally) recycled talking points. 'Israel seeks to discredit the UN' is a recycled talking point itself, of course. But I think 'HRC has bad members' is too - the UN is full of bad members. The Security Council has an aggressor state on it with veto power and everything! UN has a lot of orgs and items dedicated to the conflict? Sure, but Israel and the UN were almost born together and the conflict is one of the closest things the UN has to a foundational, OG issue - state formation, genocide, wars of aggression, right to defense, refugees, it's all there. Special Rapporteurs are kind of unserious (and why is there no Special Raconteur)? A real thing but doesn't seem clearly related to whatever interview the poster read.
Anyway, sorry for the grumptone, I just think substantive UN critique is such a fecund orchard of low hanging fruit there's not much point in settling for the frozen trope concentrate stuff.