Back in 1850s, Stephen A. Douglas and Abraham Lincoln debated with three hours speeches each. It wouldn't sit well with the attention span of modern audience.
Lincoln had to persuade people that slavery was a bad idea. We have now, largely, climbed that particular hill and are working on the next society-wide injustices.
Also, that three hour debate would be all you got. We have 24 hour rolling news now.
(I have to admit that Trump is contradicting this thesis rather badly)
It's always easy to look back and say "Why did this issue even need an argument?!".
They don't "have to", they want to
GHG on the other hand is a problem where lots of people's incomes depend on ignoring it.
It's hard to argue that the system isn't rigged when the rules of the system aren't as important as the outcome that relatively powerful decision-makers want to see.
"Marriage is between a man and a woman" was a standard for a very long time. It wasn't arbitrary. It had a really solid and complicated derivation. The Stonewall Riots were 47 years ago, but in the early '90s, even Obama and Ms. Clinton agreed with "man and woman", at least in public.
And there are still people who will hold that this is a "sin" and you can't really tell them otherwise because they use a different moral toolkit than you do.
AGW research dates to roughly 1989 - call that 27 years ago. That's not that long. It's also balanced on a very tricky spot in our economic system. It is inherently political. There's also no clear path to mitigate it beyond granting government(s) a lot of power.