Because it is the airlines responsibility and cost if you are refused entry at the destination - I can see where he was coming from - it all depends on how bad the damage was. Was the chip functional?
I had a check-in agent slightly tear the photo page of my passport - still good for 5 years. I carefull put a little tape on it to merge with the plastic sheet covering the page from the other side - and travelled that way for a while - mostly through automated gates, but also with border agents. After a warning from a border agent overseas that it was torn and asking who put the tape on, I immediately replaced the passport.