There are whole paragraphs devoted to how to let these people give their relevant first-hand experience without derailing the conversation or getting ganged up

There are whole paragraphs devoted to how to let these people give their relevant first-hand experience without derailing the conversation or getting ganged up on. That doesn't read to me like not wanting them to voice their opinion. But yes, a moderator should be concerned when groups with very different needs and motivations interact. Not because it's undesirable but because it can easily devolve into nonproductive and even harmful "discussion". It's the same concern a shop manager has when someone is new to using the table saw or torch or whatever. Except, table saws don't have a mind of their own.