Arnold Schwarzenegger Discusses Son Patrick's Miley Cyrus Romance

Arnold Schwarzenegger’s one proud papa -- not only is he hyping son Patrick’s full-frontal TV moments, but he’s also giving a nod to his past romantic choices ... even that blink-and-you-missed-it fling with Miley Cyrus.

The actor hit 'Watch What Happens Live' Monday night with Andy Cohen, and got grilled on the highs and lows of Patrick dating Miley from 2014 to 2015, and honestly ... he had nothing but kind words.

TMZ TIMELINE: MILEY CYRUS' BOYFRIENDSArnie called Miley a wonderful, talented girl and even reminisced about the time she tagged along on a family ski trip and totally charmed everyone as the ultimate guest.

As for the worst part? Arnold made it clear there wasn't one -- and…