But exposure to people all around the world isn’t going to equate to, say, making you believe in raising the minimum wage or that reparations would be great as an idea.

Raising the minimum wage I’d say is a “liberal” talking point, but I think reparations crosses the line into “leftist” territory (this is a common problem – at the danger of not having read the article, https://www.washingtonpost.com/outlook/2019/09/12/stop-calling-bernie-sanders-alexandria-ocasio-cortez-liberals/).

This ties back into my whole:

Are you sure you’re not too deeply invested in your own biases about what “a liberal” is?

The OP’s post the comment was responding to references “left-leaning” which is a spectrum, not “liberal.”

EDIT: I don’t like how this reads. What I’m trying to convey is that liberal means a lot of things to different people, and it’s got multiple definitions floating around. You may have attached ideas to that word the commenter didn’t mean, and may have misplaced feelings about what it means to “be a liberal” or to “become more liberal.”

that exposure to cultural diversity magically changes someone

I don’t think they’re claiming that at all. They’re just saying … to put it in non-political terms, if you’ve never read a mystery book before, and suddenly you’re forced to, you might change your thoughts on what a mystery book is really like.

I’ll give you, I think the comment is a bit too “racism” focused. The idea that exposure to new experiences might change your prior feelings is I think pretty reasonable. e.g., you have a bad experience with one mystery book, now reading some others might now change your feelings. It doesn’t need to be a matter of hostility, but there is an effect that quantity can have on perception… and that’s what I think “exposure” can do for a person’s perspectives.

that exposure to cultural diversity magically changes someone … that rural areas lack that diversity

This may not be true for you, but I grew up in a poor county in rural Ohio and found myself in a public high school with (per my recollection) roughly 800 white kids, 3 black kids, and no other racial identities. Things have changed there some in the years since, but AFAIK not by much.

To “out myself” and openly discuss one of those “taboo” talking points folks reference vaguely; for me, moving to the city definitely challenged some inward racism I had. It wasn’t coming from a bad place, but I just didn’t have much experience with encountering (to set the scene, at night on okay-ishly lit city streets near a bad part of town where I knew people were being mugged) big black dudes (that could’ve snapped my – at the time – very scronny self in half) in baggy dark hoodies and big baggy sweats. They sure looked like what I imagined a robber to look like, they sure looked like what I saw in movies, and they were really different from the carhartt, blue jeans, and baseball hat wearing dudes I was used to; but, the more of them that I walked past without incident, the more I realized I had a warped perception of who’s a threat.

It wasn’t just “casual racism” though, it was also things like one of my early college friends. He was as white as can be, but he wore some seriously intense gothic clothing. When he first engaged me in class, I wasn’t sure what to think, his clothes to my mind threw up red flags… SUPER friendly guy, I’m sad to say I’ve lost touch with him, but he was a genuinely great guy.

that cultural diversity is the only diversity

I agree; I can say my background doing stuff like building a vortex simulator from literal junk yard trash at my rural high school while modding Minecraft in my spare time is a pretty unique background that few others I’ve met have been able to match.

I’d wonder if the original commenter just hated rural people

And maybe; more likely, they’re just angry with them and lashing out a bit. I’m angry with how my “home town” has chosen to carry itself myself; I’ve seen lots of Democratic politicians trying to do things to genuinely try to help people, and then Republican pulling what can only be described as fraught stunts to stir up anger and piss off people in the cities or disenfranchise them. It’s a hard thing our country really needs to reconcile, way too many people are “vaguely mad that-a-way.”

and I seem to get along great with the liberal cause even though I’m not a liberal

You’re an American, we all are, and that’s what’s important. Don’t get caught up on the label on anything.