Block buttons are genuinely valuable for public safety.
kiwi farms is the most notorious of them, but there are many groups dedicated to targeting and harassing people of various demographics with the sole goal of tormenting them until they commit suicide. And they succeed far too regularly.
Communal blocklists go a long way toward negating this. Obviously they aren’t the most public, but various groups and “trusted allies” more or less share the users they block and why. I was involved with one for reddit and we are likely to set another up for the various subfederations (?) of Lemmy. The idea being that if someone triggers a red flag or two, you block them and then post their name and profile link into a google doc or a discord channel or whatever. And people either vet each entry in the list or just run a script to apply the entire blocklist to their account. So only a limited number of people need to see the assholes and people are less likely to find their feed/comments section/whatever full of people telling them to kill themselves.
Get rid of blocking and you remove that ability and people just have to “sit there and take it”. Which… has horrible consequences. Because it doesn’t matter how “strong” you are. Being told you have no worth and should end your life endlessly for months on end will wear anyone down. And while he was a right prick who did more than his share of damage, Total Biscuit put it best: (paraphrasing) You could be having the best day of your life. If someone tells you that your nose is ugly, that sticks with you.
And these hate groups make sure that those negative thoughts are all that people can think of.
And considering musk’s hatred for trans folk and minorities and the like? He knows this and this is what he wants.