Okay, so it looks like he felt he was censored by having his detailed prefacing about arming teachers distilled down to a single question. CNN deserves credit for including a prefacing argumentative sentence in the question they told him he had to "stick to".
The question about veterans seems to have been completely taken off the table.
You look at the things Cameron Kasky was allowed to say, the detailed lengths he was able to go into in his pro-gun control position, and other students were allowed a detailed preface, it gives off a weird vibe, although other students were also limited to single questions. I could have swore there were single questions, I'm trying to find them in the transcripts.
According to Haab, the sequence of events went like this: Please prepare a speech, submitted a speech. Never mind the speech, prepare some questions, submitted questions. Okay, forget those questions, here's one question we've worded out for you.
We don't have the phone call recordings, so it's really up in the air about all that was discussed, but that does strike a bit like they were open to a speech or multiple questions, especially considering other students were offered this opportunity, but then saw the speech and questions, and settled for one short question.