Code of Conducts are, for some reason, hated by a substantial portion of the tech community. For some people I think this comes down to the idea that they are silly and shouldn't be required. I entirely agree with the portion "they should not be required" and have made fun of them myself plenty when they started popping up at conferences a few years ago. Sadly, there is a reason we need warnings like "These peanuts may contain nuts" or "Hot coffee is hot". Some people are muppets, and don't know what being "not nice" is. Some people know, and don't care.
Recently in the PHP community there have been a lot of conversations about social justice, mostly fueled by the relatively recent suggestions of PHP adopting a Code of Conduct. Conversations solving problems faced by marginalized groups in PHP should be seen as a great thing, but unfortunately these conversations are not happening in a healthy way at all.