Hmm, here I am thinking I don't really care about the skin color of my neighbors. It's none of my business. But, I try and not judge people on immutable characteristics like color and age.
The important thing being conveyed is lack of diversity, not whiteness. In the United States, saying something is "mostly white people" conveys that other ethnic groups are not present for some reason (whether it be them self-selecting to not participate or because of exclusion). The purpose is almost always to note diversity or lack-thereof, and assume that the person is making a value judgement about the people because their skin is white is to completely miss the point.
For example, if you bought a pack of starbust candies, and they were almost all orange, you might note or complain that they were almost all orange. I would do so, and orange is my favorite flavor of those. The issue is, I desire the diversity of colors and flavors, and too much orange is not as good as what the added variation brings.
So, "mostly old white people" as a negative doesn't mean old people are bad, or white people are bad, or old white people are bad, but that mostly old white people are not as good as a group that has more variation in it. "Mostly" is the word you should be focusing on, not the other ones.
I would also argue that a lot of times people are called racist (or called out for saying racist things) these days are likely because people are also less likely to give others the benefit of a doubt for their actions or words. This is likely complicated in that it appears some people that do harbor racist views feel more emboldened to speak them, but I'm not sure how to pick apart how much is one and how much is the other.
edit: YES, it's a nice plan to just raise rent to cover the school taxes. However, unless you are in a popular market, your rent prices may not bear the increase. Example Northeastern PA has cheap rent because there are so many places available, and thus the $4000/yr in school tax portion of the property tax is not able to be passed on to renters.
If property taxes increased substantially, I’d have had to raise rent...
What happens when you increase property taxes is that property values go down to compensate; it's less valuable to own when you have to pay more to do it. So in the short term the property tax increase hits whoever owned the property when the rate change was announced. But then it becomes less profitable to own property in that area, so people invest less in building new housing there, or even in maintaining the existing housing. That tends to constrain supply and cause rents to increase until you're back at equilibrium. The long-term equilibrium is based on the relationship between rents and total costs. Property tax is a cost so in the long-term higher property taxes result in higher rents. (This isn't counting the pathological cases where higher property taxes reduce property values and investment and the government responds by further raising property taxes until the locality is in a death spiral. Naturally rents in dying localities tend to go down.)
In California long time landlords get Prop 13 tax cuts. New ones don't. They compete for the same tenants and charge the same rent.
Long time landlords have much bigger profit margins because of that law.
Other states have property tax restrictions but I don't know as much about them.
"Long time landlords" and "new landlords" are not inherently different people, they're the same people at different points in time. It's like saying a landlord which has paid off the mortgage on their building makes more money because they don't have to make mortgage payments. The value of the future reduction in property taxes gets priced into the purchase -- but then so does the cost of higher property taxes at the beginning, since the government still needs a given amount of revenue.
The thing Prop 13 really does is to discourage long-time landlords from selling the property at all, because the buyer will have to pay higher property tax than the seller which makes the property "worth more" to the seller, even if it's otherwise worth more to the buyer. For example, this can discourage development because the existing owner doesn't have the inclination or the capital for expansion but would demand enough for the property that it would make it unprofitable to a third party who would have to pay higher taxes.
With the way you can inherit property and keep its valuation, there may be a class of "long-time landlords"-- individuals and organizations-- emerging in major cities. Especially, as you note, since Prop 13 discourages transactions.
Well, crap, that's a fair point... But... You can't go backwards and you can't go forwards any faster than anyone else. You can't change it yourself no matter how hard you try (general relativity spaceships aside of course).