Multiple points of view POVs - why do people get so agitated?

[Worldwalker]

That has little to do with your original question, which is "why do people get so agitated?" The answer remains: I haven't seen people get any more "agitated" about it than about any other form of bad writing, and headhopping is bad writing when it makes a book hard to read.

"...if it can be got right..." is the critical part. Like the use of present tense, it very rarely is.

Switching POV is no more or less important for that group of characters in debate than any other stylistic choice is. As a counter-example, if you stay with a single POV, you can show your main character being overwhelmed by the people all proclaiming their opinions. It might work better, in fact, in creating that sense of urgency and confusion than if you were to switch POVs so that every character could mentally explain his opinion instead of just shouting it.

"Hang him high!" the skinny cowboy shouted.

"Hanging's too good for him. Drown him!" said the drifter in the corner.

"No, no, that's not right, my good people," said the preacher. "We must show him the error of his ways." That brought a few guffaws.

"String him up!"

"Tear him apart!"

Sally was starting to get a headache. It wasn't her fault that the fool had chosen to do his drinking in the Last Chance Saloon, but somehow she was caught in the middle when he got soused enough to tell bad puns.

[roseprose]

It all goes back to Aristotelian unity. A single POV simply has more unity. As authors add more POVs, they need to add other unifying devices to make good the loss. Examples of multiple POV that make good the loss might be Gail Godwin's short story, "Interstices", with its repeated and governing image of rot (frozen food melting everywhere from the basement fridge)--or the sun (time) beating down on the family reunion in John Updike's "A Family Meadow".
The biggest drawback to character switches is that sense of interfering author sticking his or her thumb in to manipulate things; such switches risk making the work seem contrived, (while implying that it is fate). Such writing risks shlock. Ah, yes, the heavy hand of fate.

[Lemurion]

The number of heads you look into in a scene is not necessarily the same thing as the number of POVs in the scene.

Omniscient means you have a single narrative perspective, which can look into any character's head. Head hopping is when you use multiple third person limited perspectives within the same scene, or paragraph, so you're looking out of different characters' heads.

Unfortunately, many people confuse omniscient perspective with multiple points of view, which leads to all sorts of problems. The key to omniscient is that you have a single point of view: your narrator. They can look into every head, but they aren't looking out from any of them. In third limited, you're looking out from various characters' heads.

Omniscient looks in, limited looks out.

While it isn't popular any more, largely because it reduces tension and increases the emotional separation between the reader and characters, omniscient is a valid technique. Switching between multiple third limited perspectives in the same scene can be done - some authors have been very successful with it - but it's very easy to do badly, and usually comes across as sloppy writing.

It's also often ineffective, especially in dramatic scenes. The key to tension is ignorance; it grows from not knowing what's going to happen next, or not knowing what the other person really thinks.

The way to build page-turning tension is to make sure neither the character nor reader knows what's going to happen next - or what the antagonist is planning to do.

Still, the most important rule of POV is that you, the writer, need to control it and not let it control you. One of the reasons certain best-selling authors can get away with "head-hopping" is because they do it deliberately to create a specific effect.

[Lemurion]

To go back to the original question of why people get agitated; it's simple: It's so easily to do badly that ninety percent of the time it's done so terribly that it drives the reader crazy.