I used to work in a lab as a technician where you were expected to do a lot of unplanned overtime (you could not leave unless the workload for the day was completed), often leading for 1 to 2 hours of overtime, and sometimes up to 6 hours. On top of that, you often had to be on call in the weekend on top of that, making a 50 hour workweek not so rare in that department.I was fresh out of school, so it did not bother that much in the beginning since I needed the money that came with the overtime.
But after a year, I got really tired of giving my entire life to that company and decided to not do as much overtime and fight back on the ridiculous schedule we were given. I would not stay on overtime unless it was absolutely critical, and I would not agree to last-minute overtime and on-call shifts. I also had to “remind” them of what labour laws are to make sure they would not try to BS me.
I quickly felt that my new attitude was not well received by a portion of my coworkers. I could tell that they felt like I was making their job even more harsh since I was not ready to “do my part” of overtime and since I refused the last-minute change of schedule it would often fall back on them (since they would never say “no” when asked).
I was also a little conflicted, because even thought I know that it's management's fault that we all had shitty conditions, if I just behaved, it would help my coworkers a little. I still decided to make my health my number one priority and go on with my new “attitude”.
I decided to talk with them and explain them how I viewed this situation. I told them that you didn't need to “love” you job, that I was there mostly to pay my bills, not because I loved the job. I have a life outside this place, and I will not let my work become my life. If we would all complain as much as I did, everyone's job would be nicer. I even told them that one of the reason I was staying was because I really loved my colleagues and that they made this place bearable.
This did not go in well. They did not tell me directly, but I could clearly sense that they tought of me as a lazy child that wasn't serious/respectful toward my job, and that I just “wasn't in my place” and suggested I find another job.
Deeper than that, I think I truly made them uncomfortable by shaking their fundamental belief that “you -must- love your job”. Our two belief system were too far away from theirs so that they just could not take my point of view seriously and decided to hate me instead. Some of them had been here for years, and since they had to deal with that for so long, they tought me as arrogant/selfish for not wanting to go trought the same treatment as them.
After that, they would still talk to me, but I could sense that they hated me a little. One of them kept saying to me that she hoped I would find a job I liked, even before I talked about leaving. I did end up leaving about 3 months after that.
TL:DR: Told my coworker I would not do overtime because I didn't care about the job, they took it as a personal insult.