'DWTS' Julianne Hough Glad Robert Irwin Passed on Chippendales

"Dancing with the Stars" cohost Julianne Hough has seen all your lusting over Season 34 breakout star Robert Irwin ... and she told us some of it might be crossing a line.

She chatted with TMZ at LAX Monday, saying, "I saw there's this older millennial group of women trying to do the math to see if that's appropriate or not." Julianne laughed before ultimately deciding ... eh, it probably isn't.

Julianne also seemed proud of the 21-year-old Aussie for turning down an offer from Chippendales to join them in Las Vegas, saying, "I think that's the right choice."

But don't get her wrong ... she definitely thinks he has the skills. "He's killing it," she gushed. "He's amazing."

In fact, she thinks "everybody on the show this year is incredible."

She continued, "I just love that everybody's watching. Thanks for watching, guys!"