Nobody's saying that. What people are saying is that gentrification takes away from a neighborhood and the identity it has, whether it be good or bad. Even NICE neighborhoods hate gentrification. Even really awful neighborhoods have a charm to them. They have shyt that no other neighborhoods have. For example, Lower Manhattan is mostly nice, and they have a lot of independent bars, eateries, etc. With gentrification, those one of a kind spots get replaced with generic ass shyt to the point where you can't tell one neighborhood from the next. Nobody likes that shyt.
Gentrification frowns upon independent businesses. That pizzeria that you grew up going to in the hood that had the best slices you've ever had, would get replaced with a Dominos. That barber shop where your barber gives you the best shape up would get replaced with a Super Cuts. That little boutique where your mother, sister, or girlfriend shop at to get their one of a kind clothes, now that would be a Forever 21 or some other big store. It removes any uniqueness to where you live, and unless you're a nomad or a person detached from society, a community doesn't want to be without an identity.