Earlier quoted context omitted.
Spamming an open source developer with angry comments because they decided to use a new tool for the code they write and publish freely is not normal.
This is rsync we are talking about. A bug in rsync basically means lost data and/or unreliable backups. I think it's normal to be pissed at lost data. Maybe it's not socially acceptable to spit in the face of a volunteer but it's 100% human to feel annoyed by an obvious drop in code quality.
Why are you hedging this? Do you think maybe it is socially acceptable?