Sufficient incompetence constitutes malice.
Veb, none of them, Redshirt aside for posting it perhaps (I don't know the history there), meant any harm. In the larger context of the PMMM fandom with the tetris meme they could easily see it as dark humor and move on. No one actually disagreed with your post - they just wanted you to calm down.
If they KEPT making light of Mami going tetris after you posted we would have an actual issue. But none of them did, people are going to view things differently. Some people here will be able to take Tetris meme as some dark humor to go along with the Mami picture responses because in the end Mami, PMMM, PMAS, etc is all just a story to them so they can make jokes about shit they likely would not do if any of this was real.
They made the joke, you objected to the joke, they stopped. I can't expect anything more than that from people. To not allow people from a huge range of background to make mistakes when interacting with each other would stifle normal conversation.
I fully expect people to attempt basic decency - but I don't expect them to know every single social landmine in a thread like this. I just expect them to stop when asked to stop.
If this is such a sensitive matter to you that the previous events are incompetence to the point of malice then I think you need to talk to those specific people who acted as such privately, possibly with a trusted mediator/referee.
I mean we had people from a dozen different backgrounds on my ship. One person's idle joke was another's insulting stereotype. We dealt with three ways. First either tell them to stop, or get someone else to ask them to stop. if they refused, or it was really terrible - then the chain of command got brought in.
If you truly think they we're malicious - talk to them, get someone else to talk to them, or get a mod.
But for the thread as a whole, can we just move on?