Your context-free formulation on the other hand provides no information for voters to weigh. Privacy or child porn detection? Well I guess I’ll pick child porn detection. Oh, you wanted to do what to my privacy? Never mind!
Even your slightly longer formulation doesn’t really explain what scanning means and how that might affect people and society. Most people aren’t familiar enough with technical and legal details to dig into the implications without added context.
It's important not to phrase it as "read your messages to detect child porn..." because that implies they won't do anything else with the messages, and Europe is a place where they still assume that if someone says they do X to do Y, they're only allowed to do Y and severely punished for doing anything else.
> Your context-free formulation on the other hand provides no information for voters to weigh. Privacy or child porn detection? Well I guess I’ll pick child porn detection. Oh, you wanted to do what to my privacy? Never mind!
you might ask questions like "How comfortable would you be with your personal mobile provider scanning your chats for child porn?" or "What would you consider to be an acceptable accuracy rate for such a scanner?". Then you could reasonably infer that respondents who say "not comfortable" or "90-100%" oppose Chat Control, because Chat Control will perform such scans and they're not 90% accurate. (Someone else who thinks the scans are 90% accurate might respond that your interpretation is wrong, but this dispute would not call the poll results themselves into question.)
I don’t think the voting result would be different if he had been even more fair about this question, as the poll is not something that MEPs are going to care about. This was clearly designed to be passed by any means necessary, and this time they got it through. But at least now people have a poll to use when they campaign to repeal it in the future, or when they want to point to the unrepresentative nature of EU decisions like this one.