I'm not sure what to tell you, except that, like the post you replied to said, "Of course [you] would think that" is a common rhetorical device in idiomatic English that in this context really, really does not mean what you seem to want it to mean. Your parent clearly does not think nor did express any statement of the form "all X are Y", and took great pains to make that, and their actual point, clear, and your "parsing" of that one sentence to make it into something close is exactly what the damn blog post is about.

I'm sorry that you feel I've trivialized mental health issues, but I will say that I've known psychotic people IRL, and again, I used the phrase "slightly psychotic" quite deliberately.