Depends.
Some students ask relevant, incisive questions that lead to clarification of an important point, or that lead to productive discussion of a particular issue. Some students ask questions that, while they might be interesting, are really somewhat irrelevant or, at best, tangential to the main issue being discussed.
I love it when students show engagement and interest in my classes. I try to devote about half of our overall class time to discussion, usually focused on assigned reading but sometimes also dealing with more general issues raised in lectures.
But i also have to get through a lot of material in a semester, and questions that take a lot of time really can put me and the whole class behind. If such questions are directly on point, and i think that they will be of interest and relevance to the students, then i’m often willing to devote some time to them. But if they’re not, then i’ll often say something like, “Well, that’s an interesting question, and i’d be happy to discuss it with you during office hours, but right now we really need to focus on the main topic of this class.”
As for the particular case mentioned in the OP, it’s a tough situation. On the one hand, it sucks that the kid is discouraged from participating because of a disability that he can’t control; on the other, the teacher has a responsibility to teach the whole class, and if one student takes up a disproportionate amount of time, then the teacher needs to find a way to deal with this. This teacher apparently spoke to him outside of class about the issue, which was the sensitive thing to do, although in her shoes i think i would maybe have started by asking him to speak a bit less often, rather than asking him to stop altogether.
Most teachers adopt strategies for dealing with any student who monopolizes class time, no matter what the cause. I had a student last semester who was very smart and engaged, and who made some great class contributions, but who also tended to go on for five or six minutes when she could have made her point quite well in one or two. I would occasionally cut her off (politely, of course) in the interests of time, and in a private meeting i told that i appreciated her contributions but that i would also appreciate it if she could be a bit more concise with the responses. She was fine with it.