There are some minority of them that are legit and good questions. But from my observations:
A vast majority of them seem to (and many clearly are) attempts to merely present one political side or another in bad light. "Actor ABC did this really bad thing XYZ. Did anyone/actor ABC do XYZ before?"
If they are phrased as "did the same thing happen", they are opinion based, as the answers would depend on subjectively deciding whether a previous occurrence was "same" or not.
If they are instead phrased as "did specific thing XYZ happen", most of the time this reflects a subjective judgement that XYZ actually happened in the first place (the recent Saudi question is on of those, with the poster subjectively assuming that the thing they claimed to happened, happened. In reality it can be argued their assessment of what happened is wrong).
And, even in this phrasing, often the answers would depend on subjectively deciding whether a previous occurrence was "XYZ" or not.
They rarely serve any purpose. What difference does it make if anyone did XYZ before? The best (and useless) use of an answer is to engage in whataboutism, which illuminates nothing about politics as scoped in this site's goals nor "makes the Internet better".