"Was Katz right?" is not the most important part. It's arguably not even relevant. If someone is presenting, and they say something that's incorrect, there are better ways to deal with it than pushing them off the platform and announcing that the Real Genius has arrived.
I can think of two right off the top of my head:
1) Wait until they've finished, then pose your correction in the form of a question to them and allow them to answer. This lets them save face (since you're not outright correcting them, you're just asking for clarification), gives them the chance to correct themselves in case they just misspoke or were misunderstood, and avoids the risk of your correction of the one incorrect point overwhelming the other, presumably correct, points the speaker made.
2) When the session is over, approach the organizer of the user group and offer to make your own presentation on the subject, in which you'll give the correct information, at the next meeting. If you're concerned that people will miss the point, add a subtitle like "A Response to Presenter X" to the name of the presentation.
> If the original presenter could effectively support his position then he would not have left the stage.
In the world of actual human beings, this is not true. People are quite easily driven to the margins by bullies who are louder and more strident than they are, even if their argument is 100% correct. Lawyers even have a saying for it: "If the law is against you, bang on the facts. If the facts are against you, bang on the law. If both are against you, bang on the table."
I can think of two right off the top of my head:
1) Wait until they've finished, then pose your correction in the form of a question to them and allow them to answer. This lets them save face (since you're not outright correcting them, you're just asking for clarification), gives them the chance to correct themselves in case they just misspoke or were misunderstood, and avoids the risk of your correction of the one incorrect point overwhelming the other, presumably correct, points the speaker made.
2) When the session is over, approach the organizer of the user group and offer to make your own presentation on the subject, in which you'll give the correct information, at the next meeting. If you're concerned that people will miss the point, add a subtitle like "A Response to Presenter X" to the name of the presentation.
> If the original presenter could effectively support his position then he would not have left the stage.
In the world of actual human beings, this is not true. People are quite easily driven to the margins by bullies who are louder and more strident than they are, even if their argument is 100% correct. Lawyers even have a saying for it: "If the law is against you, bang on the facts. If the facts are against you, bang on the law. If both are against you, bang on the table."