My sister and brother-in-law have a kid and they encourage him to feel the freedom to express himself.  It is the opposite of a 'children should be seen and no heard' mentality from an earlier time.

The trouble is that he is a kid and has relatively little ability to engage in thoughtful conversation.  He is motivated by the need for attention and frequently attempts to break up important conversations which are over his head by injecting non-sense or simply being a nuisance by making funny noises at the dinner table and such.

There are times when the kids parents simply tell him to be quite or leave the table.  This especially when the adults are having an interesting and important conversation.

This situation is very analogous to the the global climate change discussion.  For scientists and other intelligent people, the issues are complex enough and nuanced enough as it is, and the interjection of nonsense from a self-interested group (or normally from their minions) is legitimately unwelcome even among those who have a disposition toward giving everyone a voice.