Okay since there's some disagreement. Let me expand.
On one side, we have a revenue generating business, with at least one instructor, and at least one student that are leaving a door open while they go fly for an hour or two. Trying to maximize the students' time and money they leave the door open, okay it's more convenient as well. The OP sends a single text to the owner and had a single comment made to one of the CFI's, who for all we know may or may not have received it and now suddenly the users of the revenue generating hangar are declared "A bunch of lazy 20 somethings" by someone that (making an assumption here) flies a LOT less than they do. Presumably, there are 20+ times the CFI/Student do this while the OP is not present and it is not an issue, for every single time the OP is inconvenienced.
Is it a little rude? Sure. I'm not sure it is quite elevated to calling them "a bunch of lazy 20 somethings". But if they're people trying to make a buck in aviation, and I'm just a weekend warrior... you bet I am going to let them do their thing. Maybe I have to arrive 3 minutes earlier. I'm not sure it's worth all of the physical/property damage that's been advocated for in this thread. The OP still has access to his aircraft, and isn't blocked, but is minorly inconvenienced. However, if instead of CFI's and students trying to make/maximize their finite time together, if the offending neighbor was 80 and physically unable to move his hangar, it's suddenly deemed OK and it's no longer an inconvenience to the OP... so why can't that same courtesy be extended to those neighbors that are presumably crunched for time?
My comment was a 'maybe give the benefit of the doubt to the neighbors, regardless of their age rather than casting dispersions due to it' = OK Boomer. It's making a mountain out of a molehill and yelling at clouds for sure.