Gonna be very blunt here, if you mean to say that that comment is "authoritatively and confidently" saying that is misinformation to "undermine another person's comment" I have to tell you are in a very small minority that interpret that comment that way. Most people whom OP is intending to reach would read that comment as having one claim, one anecdote, and one explanation.
The claim is "macos is stable", the anecdote is "months of uptime" and the explanation is "powered by UNIX". And as the main question here is whether the explanation (which I will say is presented as a fact) is said in a manner that represents authoritative blind fanboyism or a casual statement. To preface, I think it's very clear based on my past interactions as well the upvote downvote spread that it is a casual, but factually incorrect statement. OP has experienced months of uptime and stability and attributes this to macos being UNIX under the hood.
While this is a wrong assertation, shaming is the incorrect response if the goal is to correct this misinformation. Shaming does very little to change minds and often leads to people doubling down. You will have no success with this approach. You must inform positively and confidently. Approach them from a perspective, "oh they just don't know, let me help them." Rather than "oh here comes the fanboy again, need to shame this guy". The first approach has had success time and time again and builds community. I assure OP did not seek to undermine the above comment nor did they post misinformation out of blind fanboyism they merely lack knowledge and that's how nearly everyone else in this comment chain read it.
I think just in general you may have an issue with taking things at face value and being blunt, which is not an uncommon issue. I experience this problem myself and my siblings have it worse than me though we worked past it by just learning more about language and talking to people about what they really mean when they say things. Do you happen to be neurodivergent? That's the case for us anyway.
Thankfully, bazzite is both, the community has gotten rather large lately so support has been good.