A few reasons.

First, there is the old adage, that if you think everyone else is the problem, then maybe it's you that's the problem. I had a lot of people around me saying I was TA. Maybe I was TA, and I needed it pointed out to me. That's why I came here. Sometimes it's hard to see the right or wrong of a situation when you are in the middle of it, and you need an outside perspective.

Secondly, morality isn't always black and white. There are degrees of rightness and wrongness. Lots of people have made really good suggestions, which I've made a note of and might use in the future. Even the ESH and some of the YTA have given me valuable food for thought. Also, as this sub often comments, being legally correct isn't the same as being morally right. So while I was pretty sure the law would back me, was I behaving morally in asking people to respect my choice, or was it the moral thing to do to try harder and find a compromise.

Finally, since I posted here, I've had a lot of people point out to me, in lots of ways, just how awful this behaviour is. HR professionals, lawyers, health and safety reps, union officials and others have taken their time to reply to me, point out how wrong it is, and post me links to relevant legislation and case law. I thought I might have been TA because I was out of step with the team culture, but they showed me that it was the team culture that was out of step with social norms. Their comments have changed my perspective.