Nah, definitely not the asshole. It's pretty clear that they are just upset by no longer having their laziness enabled.

One important component of assertiveness that I taught to my former clients was that everyone has an inherent right to refusal. You can say no, and you're not obligated to provide any justification.

Obviously you ought to provide context when appropriate and in work situations if you want to keep your job. But I was in similar situations where I would refuse leadership's direction on reasonable grounds/different department's duty. I would not let notorious department heads throw me under the bus, and I'd save emails to call them out on their bullshit in the email chain they lied/blamed me. I would refuse orders to over-bill and call out managers/leadership trying to push us grunts to commit medicaid fraud/waste, even in the middle of their meetings announcing the directives.

I wasn't liked by those toxic people in the organization, but they learned respect/fear me and a lot of my peers/my team would tell me they appreciated me speaking up when they were afraid to. My supervisor told me after I had her come into our boss' office with me to confront our boss over unwarranted criticism about me. Afterwards my supervisor told me: "I wish I could talk to leadership like that.. but I'm too afraid to lose my job."

I was never fired but I did leave the job when I got really sick with covid + RSV + pneumonia, a secondary bacterial infection in my lungs, pleurisy, and then long covid. The healthcare industry in my region was so strained, we had so many people quit due to toxic leadership/over-worked/burned out, and the policy was not hiring replacements and instead pushing the load on the remaining employees. I probably would've quit if I hadn't gotten sick.

But I'm proud that I always stood by my principles even when it meant disobeying/confronting superiors. My stubbornness and threshold for confrontation also made me a damn good client advocate. That was what I was most known for. I kept residential care and assisted living facilities in check, hotlining them and aiding state government investigations. It was usually stealing client funds or meds, but I also uncovered neglect and abuse.

I can be wrong and an ass at times, just like all of us. But if I feel strongly convicted about something, peer-pressure or fear of losing my job won't stop me from holding my ground.

I think you're doing the right thing standing your ground. I would appreciate you being the one to put yourself on the line for my benefit as well, if I worked in your department. That is a quality I would want in my manager. Rather than rolling over and accepting additional work/disruptions to your department's actual duties.