Not the case in my situation. Unless my Facebook circle is a complete outlier full of morons, fake news is a huge problem among older conservatives.

Yes, because we can generalize off of your specific example. It clearly is representative of all sharing.

Since you're responding to a thread about my specific example...

I'm also willing to donate $100 to a charity of your choice if you can find evidence that a significant portion, (let's say more than 25%) of fake news being shared on Facebook is just people doing it to say "look how fake this is."

What you are asking is impossible to my knowledge. I don't know of any tracking for why people share or the political affiliation of those that shared it.

This also means you argument is purely conjecture too.

Of course my argument is conjecture. I based it solely on my sample size of a few hundred Facebook friends--clearly stated.

Absent other evidence to the contrary, that is enough to convince me that people sharing fake news mostly believe it.

If you have some other evidence to present--please go ahead. Do the majority of your over 45, conservative Facebook friends and family regularly share fake news just to point out that it's fake?