Two senior showbiz executives were knocked from their lofty perches this month, their dismissals igniting sharply contrasting responses. At age 37, Scott Sassa, who ankled as president of Turner Entertainment, had already carved an important niche for himself in the community. Thoughtful, well-read and impeccably polite, Sassa is a true “insider” who will surely end up with an even more imposing title. The almost universal reaction to his departure: Why did Ted Turner ever let him go?

By contrast, Sony’s ceremonial beheading of Mark Canton produced a chorus of ridicule and denigration that defies comparison. Whenever a studio chief is dethroned, there are always mixed reviews; after all, production chiefs spend most of their time saying “no.” At the same time, many voices are heard praising the departed mogul and pointing to his slate of successes. Not so with Canton.

All of which leads any reasonable person to ask: What did Mark Canton do to deserve such disapprobation? Apart from his critics in town, even Time and Newsweek felt compelled to publish nasty obituaries of his regime. Why?

Before grappling with this, let me state that the purpose of this column is not to heap further scorn on the hapless Canton. I have never personally had an unpleasant encounter with him. In conversation, he can be engaging and even, upon occasion, self-effacing.

The son of a press agent, Canton defined his role as production chief in a rather unique way. He knew he didn’t command the presence to be a “seer” nor the attention span to be a significant creative contributor. Instead, he schmoozed the stars and filmmakers, and served as their ebullient cheerleader to a fault. Mark Canton saw every picture as a smash, whether it was “Bonfire of the Vanities” or “Last Action Hero” or “The Cable Guy.” He’d tell everyone he met that these were not just winners but Oscar contenders.

“The scary thing was that Mark really believed what he was saying,” says one long-term colleague. “He was incapable of distinguishing the winners from the disasters and knowing when to self-protectively back off.”

To Canton’s misfortune, the losers vastly outnumbered the winners, and some of his well-publicized turkeys became classic examples of studio ineptitude. Both “The Cable Guy” and “Last Action Hero” were interesting scripts in their initial drafts until the studio allowed them to veer off on weird tangents. “Canton was never there to guide, he was too busy cheerleading,” offers one colleague.

Canton’s flaws went beyond his natural exuberance, however. In an industry where discourtesy has reached the level of an art form, Canton achieved mastery over inadvertent rudeness. Even when he wanted to be polite, he didn’t know how. The stories of these “Cantonisms” are legion. One former colleague recalls being summoned to his office with a director who was in the middle of shooting a picture, only to be kept waiting a full hour in the reception room. Even as the director was computing how much his absence from the set would cost the studio, Canton peeked his head out and explained matter-of-factly, “I’m talking to a real estate agent about my house.” The door then slammed shut again as the filmmaker fumed.

I was present at one Canton meeting with a talented young filmmaker during Canton’s Warner Bros. days, when Canton decided to eat an apple. He’d ask a question of the filmmaker, then take an enormous bite of the apple, the “crunching” sound drowning out the answer. “You’re going to have to develop a much louder voice if you want to succeed as a director,” Canton advised at last, apple juice dripping down his chin. “I can’t hear a word you’re saying.”

After the well-publicized failure of “Last Action Hero,” Canton and I had lunch in his private dining room. “I have spent a lot of time discussing the film’s failure with my psychiatrist, and I feel much better about the experience,” Canton told me. “You can put that in the paper.”

I explained that such a quote might not do him any good, but he was insistent. “There’s nothing wrong with people knowing that,” he declared. The conversation served to remind me that Canton, caught up in his own narcissism, actually seemed to believe that Hollywood cared as much about his emotional health as about the health of his studio.

Mark Canton could also be amusing and insightful; he cared deeply for his colleagues and also for his movies.

But the town was changing and he wasn’t. Rudeness is no longer a way of life in Hollywood, as it was in the ’80s. Agents and artists alike want quick, lucid responses; they don’t want to languish in reception rooms or to be treated disrespectfully. In a town where too much money is chasing too little talent, civility is suddenly “in.” The intelligent, talent-friendly Scott Sassas are slowly achieving dominance over the fierce-tempered nasties who set the tone of the business community a decade ago.

No one deserves the sort of treatment that’s been accorded Mark Canton but, on the other hand, he hasn’t helped his cause by boasting that he’s going to collect his $17 million settlement and improve his golf game. Again, that’s ’80 s stuff, Mark. Get real!