Unless the initial post clearly accused *you personally* of doing X then why bother commenting to say that?
A lot of posts of the sort you're talking about tend to cite some sort of subset of humanity (let's keep it general and call that subset S) as the perpetrators of X. A literal reading of the post often does make it clear that what's meant by that is that all (or nearly all) people who do X are in S rather than that all people in S do X, but I think it's well documented that human brains do have trouble dealing with the subtleties of predicate logic and will tend to accidentally and unconsciously conflate A=>B with B=>A. Also, some posts of this type don't take care with their wording in this way and let slip some sort of indiscriminate "oh, <members of S> are such bastards" comment – and if they don't, it's a good bet that at least one of the commenters will. Either way, if a member of S reads the post, it's very easy for them to feel as if they are personally accused, inspiring an immediate desire to defend oneself.
Even I'm not immune to that tendency – and I am highly trained in predicate logic, and also have seen enough of these posts to know better. It's still not instinctive to look at a post like that and calmly think "that doesn't mean me"; the gut instinct is "hey, that means me! how unfair!" and it takes a conscious effort every time to read more carefully and think "oh no, actually it doesn't". It's a fundamental misfeature of the human brain, I fear. (One of the many.)
no subject
A lot of posts of the sort you're talking about tend to cite some sort of subset of humanity (let's keep it general and call that subset S) as the perpetrators of X. A literal reading of the post often does make it clear that what's meant by that is that all (or nearly all) people who do X are in S rather than that all people in S do X, but I think it's well documented that human brains do have trouble dealing with the subtleties of predicate logic and will tend to accidentally and unconsciously conflate A=>B with B=>A. Also, some posts of this type don't take care with their wording in this way and let slip some sort of indiscriminate "oh, <members of S> are such bastards" comment – and if they don't, it's a good bet that at least one of the commenters will. Either way, if a member of S reads the post, it's very easy for them to feel as if they are personally accused, inspiring an immediate desire to defend oneself.
Even I'm not immune to that tendency – and I am highly trained in predicate logic, and also have seen enough of these posts to know better. It's still not instinctive to look at a post like that and calmly think "that doesn't mean me"; the gut instinct is "hey, that means me! how unfair!" and it takes a conscious effort every time to read more carefully and think "oh no, actually it doesn't". It's a fundamental misfeature of the human brain, I fear. (One of the many.)