Your point was valid though. You can't let someone rock up to the stage uninvited. This would open the door to all kinds of issues.
And the original question of how the situation could have been handled better is the most interesting one. The rest is a game of he said/she said, which hn commenters tend to enjoy arguing about but is ultimately not very instructive.
With hindsight it is clear that the situation had been brewing for some time, and the conflict had been escalating slowly. Perhaps due to the pressure and stress (and time pressure) of organising an event like that nobody managed to have enough distance to deescalate it, which culminated in someone being escorted off stage by security, not a good experience for anyone.
Most likely once the invitation to talk had been rescinded the dice were thrown. It would have been hard for the speaker not to be offended, and unfair on him to expect him to take it quietly and move on without reacting. Someone should have been aware of that and worked with him to control the impact of this on his own reputation.
And the original question of how the situation could have been handled better is the most interesting one. The rest is a game of he said/she said, which hn commenters tend to enjoy arguing about but is ultimately not very instructive.
With hindsight it is clear that the situation had been brewing for some time, and the conflict had been escalating slowly. Perhaps due to the pressure and stress (and time pressure) of organising an event like that nobody managed to have enough distance to deescalate it, which culminated in someone being escorted off stage by security, not a good experience for anyone.
Most likely once the invitation to talk had been rescinded the dice were thrown. It would have been hard for the speaker not to be offended, and unfair on him to expect him to take it quietly and move on without reacting. Someone should have been aware of that and worked with him to control the impact of this on his own reputation.