I find it incredible how many people are more upset that those two got called out for their crappy views, and don't care at all what the actions of those two meant to the groups they targeted. Suppose you were a gay person working at Mozilla. How would you feel if you found out that your boss thought that you were not deserving of basic human rights?
"Would you blame them ?"
Yes, I absolutely would. Because they're adults, fully capable of taking responsibility for their own actions.
"Engaging with them is the only way things might happen."
No, it isn't. Because they do not engage in good faith. They do not debate in good faith.
"That's difficult, takes constant effort, and will require people to sustain insults"
The fact that you refer to what they're saying as merely "insults" says a lot. They are questioning the very right of these people to exist. They are questioning the ability of these people to be in public. They are questioning the idea that these people are entitled to basic human dignity. That is not just an insult to be sustained.
"Breitbart and Infowars are more than big enough to grow their audience organically."
Then they don't need the megaphone of Twitter.
"This act of censorship is doubly counterproductive even. Before we had very concrete things to point at to show how despicable he sometimes is ... and now we don't. "
This is directly contrary to your previous point, which was that they still have their own websites to get their message out.