Update: I moved all of the comments that were not deleted by commenters to chat. Your comment is restored there.
Older answer: I'll start by mentioning some context for the benefit of people who haven't read the question. Martin Hairer (chair of the ICM programme committee) asked a question about proposed topics for an ICM special lecture. David's answer started with, "A topic worthy of a special lecture, and with no obvious other place to go, is ways we as mathematicians can make our field more diverse, equitable, and inclusive."
Your comment starts as an objection to the claim that the topic has no obvious other place to go. David has clarified that he meant this in the context of lectures at the ICM, but let's assume this interpretation was not clear. Your response was roughly that diversity is a widely-discussed topic in academia, or perhaps that there are already substantial efforts to increase diversity in academia. Okay, but how is that a dissenting viewpoint? You were only addressing a peripheral point in the first sentence, and you didn't come to any conclusion about the core of David's answer.
What would your dissenting viewpoint be if you chose to write one explicitly?
- "I don't think this topic has a place in the ICM because people discuss it everywhere else"?
- "This topic is not worthy of a special lecture because I like my ICMs to be research-only/non-political/devoid of discussion about social aspects of our field"?
- "I disagree with the idea that we as mathematicians should try to make our field more diverse, equitable, and inclusive"?
- Something else?
To return to the point of your question, it seems that someone who may have read between the lines of your comment chose to flag it as "harassment, bigotry, or abuse" and a moderator then responded by deleting it. I don't know the precise rationale, but I approve of the deletion, since your comment is provocatively phrased, not particularly informative, and does not contribute substantially to a productive discussion. The fact that it got 47 votes is not absolute protection against deletion, but it does mean we weigh our options seriously.