BenderRodriguez wrote:
League_Girl wrote:
An example of a bad opinion would be thinking ADHD is a made up condition and that it didn't exist back in the days. Or a bad opinion is thinking you can turn your kids trans or that you can make your kid gay or thinking only god can heal diseases and you don't need a doctor and if you pray to god hard enough, he will fix all your problems, no need for therapy.
All bad opinions here.
It seems you're referring to uninformed, ignorant or just plain stupid opinions

(not to nitpick, but when I say "I have a bad opinion" on something I mean I think badly of it - sorry non-native speaker allert)
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This.
I am a native speaker of American English. This is correct. The expression "to have a bad opinion" means to "think less of, or to dislike, something".
Folks will describe themselves as "having a bad opinion of such and such".
The phrase is rarely used to mean that the opinion itself is of questionable quality (ie uninformed, non expert, or bat s**t crazy).
If you, League Girl, use the phrase "bad opinion" the way that you use the phrase you will just confuse folks.
If you say "Joe has a bad opinion about such and such" it will sound like you mean "Joe dislikes such and such" when what you mean is "Joe doesn't know squat about such and such, so don't listen to him". Not the same thing.
So if what you mean is "the opinion itself is of questionable quality" (not an expert opinon, or whatever) then do not refer to it as a "bad opinion". Refer to it as what it is, as a "non expert opinion". Or by whatever adjective applies to the problem with the person giving the opinion ( irrational, or whatever).