Most of my comments on reddit are replies to borderline insensitive arguments because I believe that it is very easy sound more aggressive than intended.

Generally I found that if you explain to someone how their comment might have been out of place, or maybe they just did not consider a nicer interpretation you get a nice response back.

> "you are an X, therefore your argument is junk because you are stupid/evil, here is why"

The problem with this type of comments is that generally people are not very good at complaining about them, or at suggesting better way to frame criticism. This is especially relevant in internet forums where too many personalities interact to be able to generalize and it is hard to gauge how much criticism is warranted.