Again, because you started the post because you got told that you can't say things like you want furries to die on the discord. You started the post under the pretenses that you were in some manner wronged, which you weren't by our standards. In fact the mods in the situation that you yourself documented handled it fairly well. Just because you don't agree with the rules or how they're enforced doesn't mean they were enforced wrong.
To reiterate what you did wrong and why you were told you have to stop.
You said "Furries are gross and need to die prove me wrong", you mentioned another user with the message "whats up disgusting furry" and several other remarks in the same tone.
The post was locked because you, once again, started it under false pretenses (claiming to be wronged, despite not being) and the topic itself was going nowhere as you refused to acknowledge your wrongdoings despite being asked to stop by your fellow posters. The post also started railing towards witch-hunting, even if that was not the intention, it was a part of the outcome.
The rules in the discord channel are vague to keep down the size of the message, however, their longer counterpart is linked at the top of the rules list, which expands on all of them.