Here is a short, bleak poem about how harsh judgement spreads from person to person. The speaker pictures the judgemental thoughts of the human mind as a poison that harms everyone it touches. The central image is a "hateful fog" that drifts and seeps slowly into other minds, so that nobody notices it until it has already settled in.
The speaker sounds worried and quite hopeless. The poem treats this "twisted feeling" as a kind of slow killer that picks people off "one by one" and won't stop until it has reached everyone. The short lines near the end, "never stopping," add to the sense of something relentless.
The mood is dark and uneasy. The poem doesn't offer a cure or a way out, which leaves the reader with the warning alone. Judging others, it suggests, isn't a private habit but something contagious, and the speaker seems to think the damage is far larger than we usually admit. It is probably meant as an exaggeration to make a point, not a literal prediction.