It was a lesson learned the hard way while interviewing Jamie-Lee O'Donnell on Friday night's Late Late Show.
In fairness, the host was clearly trying to pay the Derry Girls star a compliment for passing as a teenage schoolgirl in the hit show, which returned to small screens this week.
But he may have wished he could go back in time after the 30-year-old, who plays wild child Michelle in the Channel 4 sitcom, tackled his "rude" question on live television.
"This is the thing about that," Jamie-Lee 'clapped back', as anyone under 30 would say. "It gets on my nerves a wee bit.
"Do you know what it is, it's always quite misogynistic even [if] it's unintentionally misogynistic because men don't get the same scrutiny in their career."
In the interests of equality, Tubs himself is 48, although the 'young fogey' has always seemed close to 50, even when he made his broadcasting debut at the age of 12, reviewing books for 2FM.
But the praise showered on Jamie-Lee by viewers for shutting down the line of questioning shows it's still a prickly topic for women, while others seized on any excuse to get the boot into the presenter, tweeting: "Never ask a woman her age or a man his salary (€450,000)."
In his defence, Tubridy isn't the first to marvel at the ages of the ensemble cast, with Saoirse-Monica Jackson, who stars as 16-year-old Erin Quinn, the baby of the bunch at 28.
While if I were her co-star Nicola Coughlan, who also plays 17-year-old Penelope Featherington in Bridgerton, I'd be shouting the fact that I'm 35 from the rooftops.
Yet the car-crash exchange speaks volumes about the persistence of ageism in showbiz.
Recent film industry analysis, as an example, found that while the percentage of female characters in speaking roles ticked up between 2019 and 2020, just 16 per cent were in their 40s, compared to 28 per cent of male characters, and even fewer - six per cent - aged 60 or older.
It's an age-old trend that in 2004 inspired Geena Davis to set up the Geena Davis Institute on Gender in Media, which advocates for equal representation of women on screen from age to race and body type, with the Oscar winner previously recounting how she had been told by a male actor 20 years her senior that she was "too old" to play his love interest.
That the casting of then 50-year-old Monica Bellucci as a Bond girl opposite Daniel Craig, then 47, in Spectre in 2015 was regarded as ground-breaking proves how embarrassingly slow attitudes are to change.
Admittedly, in my twenties, I never really understood why some women are so precious about revealing their date of birth.
Now, with a couple of years on Jamie-Lee, I have to admit I get it.
Celebrities like J Lo (52), Jennifer Aniston (53) and Elizabeth Hurley (56) may be rocking middle age, but for the rest of us, the so-called 'age of invisibility' sadly hasn't disappeared.