But, former Chicago Cubs star Mark Grace must've missed that lesson ... and now he's apologizing for his bizarre rant during Saturday's game.

The 56-year-old joined Len Kasper and Jim Deshaies in the booth (virtually) for the Cubs vs. Brewers game on Marquee Sports Network over the weekend ... when he was asked to give a fun story about his playing days.

That's when Grace couldn't help himself but call his ex a "dingbat" several times while sharing an incident where she accidentally parked in a spot reserved for then-Brewers owner Bud Selig ... forcing Grace to rush out in full uniform to stop the car from being towed.

"My ex-wife, I’m going to go Archie Bunker on you guys a little bit," Grace said on air, "I called her the dingbat."

For those who don't get the reference ... Bunker is a character from "All In The Family" and "Archie Bunker's Place" ... and the guy was known for calling his wife -- you guessed it -- a "dingbat."

BTW -- While Kasper and Seshaies awkwardly played off the comments, neither spoke up and said Grace's jabs were a bit off.

To make matters worse, it wasn't even a good story -- she parked in Bud Selig's spot decades ago ... who cares?

Grace later apologized for the bad TV moment ... saying, "During today’s game I referred to my ex-wife in a way that I absolutely should not have."

"I want everyone to know how very sorry I am about that. My remarks were offensive and inappropriate, and I deeply apologize.”