TORONTO, Sept 14, 2009 (AFP) - Is honesty always a virtue, and should you ever call the US president a liar?

Not when it hurts a peer onstage at an MTV Music Awards show, and not during a presidential speech to a joint session of Congress, Hollywood actors Rob Lowe and Jennifer Garner opined Monday.

The pair, speaking to reporters at the Toronto film festival launch of comedian Ricky Gervais's new film "The Invention of Lying," set in a parallel universe where lies do not exist, blasted Kanye West for his attention-grabbing bout of honesty at the MTV awards show on Sunday.

The rapper crashed the stage during teen star Taylor Swift's acceptance speech to say he felt Beyonce should have won the award.

It is okay to lie "to save somebody's feelings, or if someone asks 'How are you?' I think it's perfectly acceptable to say 'fine' if you're not and you don't know them well," Garner said.

But West's outburst was "not honesty. It was just bad manners," she said.

"What is the point of going through the day and thinking that it's cool to wear your honesty on your sleeve at the expense of everyone around you?"

West stunned audience members during Sunday's extravaganza in New York after country star Swift, 19, won a statuette for best female video for her hit song "You Belong With Me."

Lowe, for his part, reproached a Republican lawmaker for shouting "You lie!" during President Barack Obama's recent primetime health care speech.

"Regardless of how you feel, (for the sake) of civil discourse, you just don't do that on the floor of Congress," Lowe said.

Lawmaker Joe Wilson, meanwhile, has apologized to Obama for his outburst.