Anecdotally people in their mid/late twenties + thirties are often the most tolerant. Teenagers and young adults are often more extreme in their views and hence often less tolerant.
I'd argue the reason some grow less tolerant in the later half of their life is just that people often just stop giving a shit.
I'd argue the reason some grow less tolerant in the later half of their life is just that people often just stop giving a shit.