If you look at the facebook newsfeed algorithm—a technology widely regarded as evil—then it can be considered a form of automated AI-based blocking. While the mechanism to create an echo chamber of only things you agree with is different, it achieves that same end result.
I think everyone should have the right to block whomever they want, and utilize whatever tools that make it easy for them to do so. However, just like with a gun, you can easily shoot yourself in the foot with this. Twitter here would be like the gun manufacturer, except instead of guns, they are making user features that make it easy for people to shoot themselves in the foot.
If I were the one making the tool, I would feel morally responsible for providing such an evil tool. Because at the end of the day Twitter is like Youtube which is like TikTok which is like Fox News. They show their respective users exactly what they want to see and it increases their bottom line, even if there are negative long term repercussions to society or to the users.
My goal would be to carefully design a product that engages people with their peers, even when it's unpleasant, while moderating away true harassment in a separate fashion.
While easier said than done, I do not believe the tools designed to remove spam or harassment should be the same tools to silence dissenting voices. My main contention is not that people should not be able to block spammers and harassment, but that such an easy and indiscriminate application of some tool like this has long term negative repercussions for society, as well as one person's mental health and development.
Hacker News used to have downvotes for posts. They removed that after some discussions around it here, and I applaud that. I think having a flagging feature to indicate spam and up-vote only is a good implementation. Unpopular ideas at best disappear (to be resubmitted again), but they cannot be actively buried like they used to be.
How do you think cults, or regimes like North Korea, work? They block out outside influences.