There is of course, some effect but it's relatively minor for the middle class. Someone who's making a good income is not going to settle for the same conditions an illegal immigrant does, they're not competing in the same market. Your analysis leaves out a bunch of realities, for example: Most illegal immigrants share housing, reducing pressure compared to the normal. They also tend to stick to immigrant neighborhoods due to language barrier and need for cash transactions, this reduces their impact outside these areas. There is such a thing as homelessness more population on the lower income scale doesn't always mean that property values go up due to resources being taken since some will end up homeless. People tend to get the best they can afford, if illegal immigrants are taking the lower end of the market the legal people aren't just going to start buying "better" places.
Illegal immigrants have a negligible effect on the property values of the type of property people putting up walls and fences around their homes own. And lastly I highly doubt anyone who's against the border wall is realistically thinking "this will keep my property values up!"
They can lessen competition by not building a big hub in an airport that that's already a hub for a competing airline. If they avoid stepping on each others toes with hubs there are less airlines to compete on price with. If Minneapolis is a hub for Delta, then they have a virtual monopoly for all the smaller airports in the area that need to first fly to Minneapolis before the final destination.
It's about supply and demand and fuel efficency. A small airport between Albany and NYC won't have enough people to fill a plane capable of flying to LAX efficiently from a fuel perspective, so they'll take a flight to NYC first then the LAX on a bigger plane that can spend less per person per mile to get there. Larger planes tend to be more fuel efficient (assuming all seats filled) than smaller ones which is why hub and spoke model makes a lot of sense. The 787 is actually abnormally fuel efficient for its size and it's opening up many direct routes that were previously not economical since it's a smaller plane that costs the same per mile per person as much larger planes.
Illegal immigrants have a negligible effect on the property values of the type of property people putting up walls and fences around their homes own. And lastly I highly doubt anyone who's against the border wall is realistically thinking "this will keep my property values up!"