Can my employer demote me because I have an FMLA approved disability?

I have become partially disabled with a chronic autoimmune condition (which isn’t visible) and had to take FMLA (specifically intermittent leave) to assist me. My condition and subsequent absences are constantly brought up and discussed by my team, the other employees in my department have told me “yeah management staff are fed up with you taking time off.” Another informed me that they joked about the condition and even roll eyes and make comments “what is it this time?” When i have called out from work. And though management hasn’t said any of this to me, it really sucks. 1 month ago I was informed me that they would be reducing my duties, by giving up duties at one of the divisions I work at to an employee they were promoting to be a divisional worker instead of a corporate help desk worker, and i was asked to train him to be a backup at my division “just in case my absences continue”. This week i was informed that I was being moved into the former position this new person held which has reduced duties (helpdesk technician) and he would be be assuming my duties. This new role at a different division for me is in another city entirely, which I have trouble traveling to as the bus system doesn’t get me there, and I’m unable to drive most of the time. When I informed my supervisor that I would be unable to take that position, I also asked if my position was being eliminated, and he said “No, you’re position isn’t going away we’re switching roles as a training exercise, indefinitely”. I asked if I was the only individual from my team being being cross trained and was told yes, you’re the only person it makes sense to move in this manner, but he refuses to give me a start or end date of the training. I asked who would be cross training me and was told no one, he didn’t have the staff to do so I’d just have to learn the new position by doing it, but since I’ve been on helpdesk a before it shouldn’t be a problem. I have explained that my doctor has advised me not to travel by driving, and my supervisor scoffed, and said I can’t believe that you’ll have a problem driving 20 more minutes each way, but I’ll make sure I tell HR and our leadership team you’re unwilling to do the job I’m offering you. Aside from being bullied, which isn’t illegal, I am being singled out, should I contact a lawyer at this time? How do I do that without any hard copy proof?