You just knew this discussion was going to be a tad contentious:

Any time one of the country's most famous Catholics sits down with one of its most outspoken atheists just days after a terrorist attack motivated by religious extremists, sparks are bound to fly.

And that they did Monday on "The Late Show," when Stephen Colbert welcomed fellow late-night host Bill Maher of HBO's "Real Time."

Maher began his appearance by arguing the only way to wipe out groups such as Islamic State is to "wipe out the idea" that motivates them -- an idea that Maher believes is held by many mainstream Muslims, not just the extremists.

"We have to change those ideas, women as second-class citizens, gay people don't deserve to be alive," he said. "These are mainstream ideas unfortunately."

The remarks, typical of Maher's anti-religious standpoint, prompted an observation from Colbert.

"They say at a dinner party you should never talk about sex, politics or religion. Have you ever been invited to a dinner party in your life? Are there things you won't talk about?"

Maher responded that he'd be unlikely to get a dinner invitation from Colbert anyway, since the men are "very opposite" when it comes to religion.

Though Colbert admitted that he is a practicing Catholic, he quickly added, "It doesn't mean I'm good at it." He also attempted to lure Maher, a former Catholic, back into the fold.

"Come on back, Bill," he said. "The door is always open. Golden ticket, right before you. All you have to do is humble yourself before the presence of the Lord and admit there are things greater than you in the universe that you do not understand. Take Pascal's wager. If you're wrong, you're an idiot, but if I'm right, you're going to hell."

Maher wasn't buying it: "I do admit there are things in the universe I don't understand, but my response to that is not to just make up silly stories, or to believe intellectually embarrassing myths from the Bronze Age, but you believe whatever you want to."