Just as beauty is in the eye of the beholder, so too is negativity. At least, that's true when it comes to so-called negative attack ads.

What I mean is, whether or not you view a political ad as "negative" often depends on your partisan political point of view. For example, the NDP recently released what I would consider to be a classic negative TV attack ad.

In fact, it's so blatantly negative it almost comes across as an attack ad parody. For one thing, the ad features an extremely unflattering photo of Prime Minister Stephen Harper; it's so unflattering one commentator said it makes Harper look a sweating dog.

Plus the ad makes over the top claims, such as when it says Harper led Canada into a recession. In other words, it has all the traits associated with attack ads. Yet when I went on Twitter and described it as such, I was immediately met with protests.

NDP supporters assured me the TV spot in question was not an attack ad at all! This didn't really surprise me.

After all, it's just basic psychology. Negative ads have a certain stigma and we just don't want to believe "our side" would do anything bad. The other guys might run negative ads, but we don't. Besides, if we agree with the message in the ad it can't be negative. And by the way, this bias doesn't just apply to NDP supporters. The same goes for other political partisans.

Last year I wrote a column in which I scolded the Conservatives for their infamous "Just visiting" attack ad which targeted former Liberal leader Michael Ignatieff.

Recall, that's the ad which questioned Ignatieff's patriotism and integrity. I called it a "mean-spirited, personal attack.",Guess what? Not long after that column appeared I received emails from outraged Conservative Party supporters defending the ad.

One guy told me the spot was not negative because it was just telling the "truth." And that's the usual defence when partisans defend their party's negative ads. They will say something like, "It's not negative, it's just honest." Or "There is nothing wrong with this ad because it's based on facts."

Of course when you think about it, that's not much of a defence.

After all, a vicious negative attack ad can also be truthful and based on facts. Indeed, the best attack ads are carefully sourced. When the Conservatives used ads to attack former Liberal leader Stephane Dion for his plan to impose a carbon tax, it was factual. Dion did want to impose such a tax.

The other defence partisans like to use for negative spots is to severely restrict the definition as to what constitutes an attack ad. They say an ad is only an attack ad when it engages in character assassination. In other words, unless an ad comes right out and calls somebody a Satan-worshipping, wife-beating, fascist-loving pervert, it doesn't count as an attack.

Of course, under that strict definition attack ads would be extremely rare. That's because in most such ads the attack on character is implied rather than overtly stated.

Take the NDP ad mentioned earlier. It supposedly just criticizes Harper's policies. Yet at one point in the spot the narrator says Harper's solution to our economic downturn is to attack Canada's most "vulnerable" citizens when they are most in need.

Doesn't that suggest that Harper is unfit to govern because he's a callous, unfeeling politician? And isn't that an attack on his character?

At any rate, there's nothing to be done about partisan bias. And this is why people who want to ban "attack ads" face such a steep uphill battle. How can you ban something political partisans don't believe exists?