Text has a pretty low bandwidth. You don't get to see facial expressions, body-language cues, or anything else beyond the words actually written. Which means you have to be really careful about projecting stuff onto it that might not actually be there.

I've been corresponding with people by email and newsgroups/forums for 25 years and I still occasionally get caught out by this.

(... which is not to say that the perceived animosity isn't there, just that unless you know the author pretty well in other contexts, you won't always know for sure. Somebody making a factual statement that [you think] makes you look bad may not initially be intending to denigrate you, though if you answer with sufficient venom, they may well become motivated to where they weren't before...)