https://us.forums.blizzard.com/en/wow/t/politics-in-trade-chat/649428/6
That’s what YOU can do.
If you feel that one or more people are spamming a topic in chat, report them and ignore them. Or simply create your own channel and move to it, so you don’t see any of it during your time in a Trade chat hub.
And creating new official channels - people come up with this idea now and then without ever showing a way to control who talks in it about what.