That kind of thing pisses me off. When did it cease to be the captain's airplane, and become the gate agent's airplane?
I had a gate agent do that to me years ago, claim it's "their aircraft at the gate". I asked the question, if you, the gate agent ram the jetway into the aircraft and cause damage, are you allowed to make an entry into the aircraft logbook? Needless to say he didn't have an answer to come back with and his attitude went bye bye.