When Steem was quite new, flagging was discouraged except for "abuse." But I have been here a long time, and I have been flagged not by witnesses but by other users without an explanation.

I am not crying here, really. It's just that I bet this is not just my experience and for some it probably is much worse for them. If Justin Sun is arguing that he is going to get rid of downvoting, he is going to get support that way.

Look at this post of mine:
Global Temperatures

Two down-votes: no explanation

One in Spanish, about Bitcoin in ARS. In retrospect, I hope no Argentinian bought BTC

Two down-votes: no explanation.

Not that I tend to get down-votes a lot, some subject matters bring this but the point is, I can empathize with the frustration for someone who is getting a lot of down-votes on his or her account on every other post.

You need to address why downvoting is good. Whaleshares is the best example why downvoting is good but its not enough to argue.

In UIs, instead of just a (V) to down-vote, have several down-vote buttons with each an explanation: A button that says "flagged because the content is pornographic", one that says "flagged because the content is hatespeech", another one that says "flagged because the content is a personal attack" (and is not about Justin Sun), yet another that "flagged because its fakenews", pen-ultimately one that says "flagged because its getting too much money", and finally one that says "other reason". At least a little transparency into the thinking of the flagger might be helpful. It might cause some introspection on part of the flagger as well. This can all be done without changing the consensus of the chain.