You can as easily argue the opposite: older people can be more conscientious because they have less to gain and less to lose. Who cares more about a payoff: someone who already has their gains and fewer years left, or the hungrier younger person?
I suspect you have based your “fact” on sampling bias - we don’t get good visibility metrics on young corrupted politicians (not so many young politicians, not so much time for them to have been caught making egregious errors). Disclaimer: middle-aged engineer type.
How many people in their tweens to 40th have ever filled the roles they were talking about? That's the only timeframe this argument would make sense to me.
I really can't see their comment as bigoted as you claim. There really is a strong selection bias with people filling these roles at that age and them behaving like that. That's doesn't mean that people in that age braket are always corrupt, but people that have been in these roles for extended periods of time generally are corrupt.
Representatives, whether young or old, never face the consequences of their actions because they exist in a separate system from the rest of society. They have special health care, private schools, and so on.
Sure, a 65-year-old age limit would exclude some candidates who get into politics at a later age, or who are uniquely gifted. But there are plenty of examples from across the political spectrum of people who should perhaps move on to write their memoirs instead of running for that nth term.
Average age of US citizens is 38.8 years. I don't think this needs to be exactly the same & I think it's good for senators to skew older as wisdom accrues with age, but this doesn't simply mean "older is better."
Mostly I think it would be good to build the next generation of leaders periodically. Senate seats are and congress are zero-sum, the next person can't get into that seat until someone else gets out, and those "years as a legislator" are important to operate effectively.
1: https://crsreports.congress.gov/product/pdf/R/R46705#:~:text....
I'd be in favor of a two-term limit personally, for many of the same reasons. If it's good enough for the President it should be good enough for other offices. I don't think political office should be a lifetime career. It attracts too many power-seeking, controlling personality types. We don't need those people around forever. Too many people in office have no private sector experience at all, yet they are making the rules that the rest of us live by.
We have a census to grow the numbers in the House, but they passed a law to stop that.
"The Number of Representatives shall not exceed one for every thirty Thousand..."
"Representation based on population in the House was one of the most important components of the Federal Constitutional Convention of 1787."
https://history.house.gov/Institution/Origins-Development/Pr...
And yes, as people age, they do tend to suffer cognitive decline. You may be the exception, but as a rule it's still a factual statement.