The Davis Square Community

Preventing gentrification is difficult. To a considerable degree, Prop. 2 1/2 (in Massachusetts) limits the increase in taxes on homeowners, which prevents homeowners from being priced out of their houses. I don't know if it protects landlords as well; landlords might get stuck with large tax increases, which they will pass on to their tenants. Of course, if the actual market value of an apartment rises, landlords will generally raise the rent correspondingly. Rent control measures can prevent that (and will thus prevent the increase in the value of the property). But rent control has been outlawed in Massachusetts.

I gather that San Francisco has strict rent control, but the difference between the market value of apartments and the rent controlled value has become so high that people are engaging in many devices to escape rent control, and gentrification is proceeding anyway.

In the long run, it's difficult to stop. The only political mechanism that would work reliably is to make the area less desirable to live in for people who are more affluent than those who live there already. Politicians can do that if they work at it. Mob violence doesn't work very well because there isn't a specific set of actors who are driving the process, the culprits are all the people who are willing to pay "more money" to live there.