Almost every audience will have a difficult audience member. It is not what you want to hear, but it is the truth.
This is the person who is cranky for no apparent reason. This is the person who is known by colleagues and coworkers as being difficult and negative 24/7. This is the person who frowns at puppies, rainbows, or sunflowers. And the fact of the matter is you cannot control that person or what he/she says.
All you can do is control your response to him/her, which means you remain cool and calm and ignore the person's attitude for the most part. (Do not ignore the person. Ignore the attitude.) Oftentimes, if you are doing a great job with your presentation and others see that, because colleagues know this person to be something of a trouble-maker, they will address the person for you. And even in an audience where no one knows each other, if you're doing an outstanding job, you will have others who recognize this person is simply being difficult, and you may have a situation where that person gets isolated by the majority.
However, it becomes a real issue for the presenter when the audience or a heckler has some very good points that he/she brings up but for which you have not entirely prepared to address or simply did not anticipate that point would arise.
The operative phrase is "you have not entirely prepared," and here is how you address that: Ordinarily, I would write you must always be prepared, but I realize we are humans with full plates. I also recognize you cannot be an expert on everything or time may not be on your side, precluding you from investigating every single angle of a topic.
What you do is choose three aspects you will address and on which you become something of an expert, and share those as part of your agenda items or as part of your objectives when you begin your presentation. When you get a heckler who is an expert (try not to think to yourself, "If you're such hot stuff, then why didn't the coordinator of this event get you up here to speak?"), say to the heckler "In the interest of time and focus, I will address only these three components. You and I can certainly have a conversation offline about what you have brought up."
Then put the onus on the heckler to reach out to you: you provide your contact information; do not ask for his/hers. If the point is really important, then you will hear further from him/her; if not, then no worries.
Remember if the presenter has not done a good job of providing the audience with useful information, a good job of wisely using the audience's time, then the majority of the audience will check out or some members of the audience will become difficult. As I once read from Jason Teteak, CEO of Rule the Room Public Speaking, the audience has to "feel" the presenter before it will be cooperative and engage. However, if the presenter has not demonstrated his/her expertise, if he/she has not addressed an elephant in the room, then hecklers will crop up. When frustration comes down, listening goes up.
The best advice I can give everyone is to plan your presentation so there are always opportunities for the audience to remain engaged and attentive and, therefore, poised to forego trying to derail your efforts. And as you plan your presentation and constantly be aware of what you want your demeanor to communicate and how you come off to others at all times - as if you are on live TV - so, no matter the disruption, you are clearly pulled together, professional, and polished.
And if you liked this post, you may also enjoy "Handle the Toughest of Questions Like a Pro."