I think the 'eyes bleeding'-type comments come from the author's rewriting sed in javascript. It seems almost like an exercise designed to provoke: rewriting one of the cornerstone nix utils (loved by many nerds everywhere) into a node.js package (despised by many nerds everywhere).
Like any good conversation starter, replace.js comes with a bit of incorrect information:
It's similar to sed but there are a few differences:
1. Modifies files when matches are found
Easy enough to do with sed: -i
2. Recursive search on directories with -r
find . -exec sed [...] does the same.
--
In my estimation, that's the reason for the vitriol. I am intentionally leaving out any analysis on the morality of the reactions to it, but the above should explain why some reactions were less than great. It wasn't about the code itself.