Note that I'm using the term "disgust" as a mild variant for toxic behavior. After all disgust is the provoked reaction towards toxicity.
There are always some shitheads online, I personally recommend just ignore those who you believe do behave in a disgusting manner but with the caveat that you must lead by example yourself. After all, there are very specific profound psychological reasons to find something abhorrent or disgusting.
However, people may have different degrees to what accounts as a disgusting action, so their reason may not align with yours. Its best to just let people have their opinions, so don't point fingers and behave yourself according on how you want others to behave. So in the end, if you inspire enough people there is a huge chance that people intrinsically attempt to understand your viewpoint, which means that implied toxic behavior may simply vanish over time. Because if you lead by example you may open peoples eyes towards the problem.
But if you just point fingers and say that "people are evil", then you're just making things worse for others but also for you, because you contribute to an atmosphere that is always fluctuating, which makes things even harder to pinpoint any problem, which leads to people having even less of a clue regarding the actual problem you may think the forum has.
Instead of making a thread, just engage with people in random conversations. Help people, be nice to people and enjoy the forum. You will see that in due time, those you may think of as toxic right now are actually not-so-bad folks after all.