|This page in a nutshell: If someone is in a legitimate content dispute with you, don't call them a vandal. It makes you look stupid.|
Vandalism (n.) – Willful damage or destruction of any property with no other purpose than damage or destruction of said property.
It includes youths who break the windows of a house during a riot; it doesn't include someone who destroys a house in order to create a highway, no matter how bad of an idea the highway is.
The same concept exists on Wikipedia. An editor committing vandalism is one who tries to compromise the integrity of Wikipedia just to get a kick out of it. It does not include misguided or obtuse editors who change a page because they genuinely want to improve it. If you are referring to such edits as "vandalism", then you are misusing the word.
One day Little Suzy was in the car coming home from kindergarten class, when she saw a man spray-painting an obscenity on a street sign. When she pointed it out, her mother barked, "I can't stand people who do that. The police really should crack down on those vandals!" Suzy didn't understand the word vandal, but was determined to figure it out. Later that night at the dinner table there was a political argument. Her mother felt very strongly, so she again barked "I can't stand politicians. They're ruining our country." So Suzy thought the politicians must be vandals too! After all, Mom hates them both and they're both ruining something.
Little Suzy's reasoning of course is flawed. In philosophy it's known as the fallacy of the undistributed middle. Politicians aren't actually vandalizing with their policy, even if Suzy's Mom thinks they're misguided.
Sadly, Wikipedians often level the charge of vandalism against anybody who makes edits they don't like, including good faith edits or POV pushing. However, good faith edits and POV pushing are not vandalism, and just because a person disagrees with you does not mean he is acting in bad faith. Sometimes a newcomer may simply not know the difference, but having a long-time editor who mislabels an edit as vandalism says more about the accuser than the accused. Here's a short list:
Almost invariably, these problems show up in other aspects of the accusers' behavior: they don't take the other side's argument into consideration; they edit war excessively; they're dense.
In short, if you're in a content dispute with someone, don't call that person a vandal. It makes you look stupid.